List of The Big Bang Theory characters

The American sitcom The Big Bang Theory, created and executive produced by Chuck Lorre and Bill Prady, premiered on CBS on September 24, 2007. The series initially centers on five characters: roommates Leonard Hofstadter and Sheldon Cooper, two Caltech physicists; Penny, a waitress and aspiring actress who lives across the hall; and Leonard and Sheldon's friends and co-workers aerospace engineer Howard Wolowitz, and astrophysicist Raj Koothrappali.

The Big Bang Theory cast at Comic-Con 2009, from left: Kunal Nayyar, Simon Helberg, Kaley Cuoco, Jim Parsons, and Johnny Galecki

Over time, several supporting characters have been introduced and promoted to starring roles, including Bernadette Rostenkowski-Wolowitz, Amy Farrah Fowler, Stuart Bloom, Emily Sweeney, and Leslie Winkle. The series also features numerous supporting characters, each of whom plays a prominent role in a small group of episodes. Included among them are parents of the main characters, their dates and their coworkers. Celebrities such as Stephen Hawking occasionally appear in cameo roles as themselves.

Character appearances

Character	Portrayed by	Seasons
		1	2	3	4	5	6	7	8	9
Main characters
Leonard Hofstadter	Johnny Galecki	Main
Sheldon Cooper	Jim Parsons	Main
Penny	Kaley Cuoco	Main
Howard Wolowitz	Simon Helberg	Main
Raj Koothrappali	Kunal Nayyar	Main
Leslie Winkle	Sara Gilbert	Recurring	Main	Guest						Guest
Bernadette Rostenkowski-Wolowitz	Melissa Rauch			Recurring	Main
Amy Farrah Fowler	Mayim Bialik			Guest	Main
Stuart Bloom	Kevin Sussman		Recurring				Main	Recurring	Main
Emily Sweeney	Laura Spencer							Recurring		Main
Recurring characters
Kurt	Brian Patrick Wade	Recurring
Dr. Eric Gablehauser	Mark Harelik	Recurring
Mary Cooper	Laurie Metcalf	Recurring		Recurring				Recurring
Mrs. Wolowitz	Carol Ann Susi	Recurring, voice only
Dr. V.M. Koothrappali	Brian George	Recurring							Recurring
Mrs. Koothrappali	Alice Amter	Recurring							Recurring
Stephanie Barnett	Sara Rue		Recurring
Barry Kripke	John Ross Bowie		Recurring
Beverly Hofstadter	Christine Baranski		Recurring			Recurring		Recurring
Wil Wheaton	Wil Wheaton			Recurring
Zack Johnson	Brian Thomas Smith			Recurring				Recurring		Recurring
Priya Koothrappali	Aarti Mann				Recurring
President Siebert[lower-alpha 1]	Joshua Malina				Recurring
Mike Rostenkowski	Casey Sander					Recurring				Recurring
Alex Jensen	Margo Harshman						Recurring
Janine Davis	Regina King						Recurring
Lucy	Kate Micucci						Recurring	Guest
Arthur Jeffries	Bob Newhart						Recurring			Guest
Dave Gibbs	Stephen Merchant									Recurring
Claire	Alessandra Torresani									Recurring

Original main characters

Leonard Hofstadter

Johnny Galecki

Leonard Leakey^[1] Hofstadter (Johnny Galecki) is an experimental physicist with an IQ of 173 who is originally from New Jersey and received his PhD at age 24, spending at least some of his time at Princeton University. He shares an apartment in Pasadena with colleague and friend Dr. Sheldon Cooper. Unlike his equally geeky friends, Leonard is interested and quite adept in building interpersonal and social relationships with others. Compared to his friends he is relatively successful with women. The writers have toyed with a romance between him and next-door neighbor Penny since the pilot, with their unresolved sexual tension being a major force for drama. Leonard dated Penny for most of season 3, although they had dated briefly at the end of season 1. Aside from Penny, Leonard has had romantic relationships with coworker Leslie Winkle, physician Stephanie Barnett, an unnamed French literature PhD, and North Korean spy Joyce Kim. Following his breakup with Penny, Leonard began a relationship with Raj's sister Priya in season 4, and it is implied they had a brief sexual encounter before the start of the series on an occasion when Priya visited Raj. The two attempted a long-distance relationship after Priya moved back to India, but Leonard eventually broke up with her in season 5 after she admitted to cheating on him with her former boyfriend. In season 5's "The Beta Test Initiation", Leonard and Penny start dating anew though their relationship is rocky. Over the next two years they talk of marriage and each have unsuccessful proposals until the end of season seven when they become engaged and get married in the season nine premiere. Leonard's family includes other accomplished scientists: his mother, Dr. Beverly Hofstadter, is a world-renowned psychiatrist, his sister is a biologist and his father an anthropologist. Also, his brother Michael is a Harvard law professor. It is mentioned in the season 2 episode "The Maternal Capacitance" that Leonard is the least successful member of his family. He is also known to be lactose intolerant and cannot process corn, as Sheldon states in "Pilot". Leonard also plays the cello.

Sheldon Cooper

Jim Parsons

Sheldon Lee Cooper (Jim Parsons) is a theoretical physicist, possessing a Bachelor of Science, Master of Science, PhD, an ScD, and an IQ of 187. Originally from East Texas, he was a child prodigy, starting college at the age of 11, and receiving his PhD at age 16. He is usually cold, selfish, calculating, and immature, but at the same time it's in a well-meaning way, it's not on purpose, he just doesn't know any better. He does have a softer side, as he does in fact care about his friends, and loves his mom, grandma and girlfriend, Amy, even though he often insults them with either about their intellect level or different opinions. Sheldon refrains from any form of physical contact if possible and exhibits a strict adherence to routine to the point of exhibiting obsessive–compulsive personality disorder, performing specific activities on specific days and specific times, such as doing the laundry on Saturday night at 8:15. Any disruption to this routine distresses him enormously. A running gag has him always knocking on doors or other surfaces in a pattern of three knocks and one call repeated three times, which he has the urge to complete no matter what. He has forced Leonard into signing an absurdly exhaustive "Roommate Agreement", and later enters a similar "Relationship Agreement" with Amy Farrah Fowler. Sheldon has great difficulty identifying sarcasm and irony and responding in kind, and a recurring topic is his efforts to acquire these skills. He has also enormous difficulties lying or even keeping a secret, giving himself away with wild facial tics and implausible statements. He is however fond of occasionally playing a prank, which he typically punctuates with his trademark exclamation "Bazinga!". Sheldon has a superiority complex and makes no effort to hide his contempt for other people's intellects, often making highly inappropriate comments. A common joke is his inability to drive, although he did receive a learner's permit.^[2] Sheldon loves comic books and science fiction like his friends, but to the point of being obsessed about them, and is a fan of Spock, a fictional character of the Star Trek franchise.^[3] Unlike Leonard and Raj who come from intellectual families, Sheldon stands out from his own relatives. His father, George, whose death pre-dates the series, was described as a stereotypical Texan who liked football, skeet shooting, and heavy drinking,^[4][5] his mother, Mary, is a devout Evangelical Christian, who does not seem to understand her son's fields of study, although she does displays common sense and intelligence;^[6] his twin sister, Missy, and as-yet unseen brother, George Jr., were both described by Mary as being "dumb as soup". His fraternal twin sister later has a baby boy, making Sheldon an uncle. He meets Amy Farrah Fowler in the season 3 finale and starts a highly unusual and very slowly evolving relationship with her, and by season 7, they start kissing each other. Previous to this, he had exhibited some affinities with Leonard's equally unemotional mother. In the season 8 finale, Amy breaks up with Sheldon, but Sheldon reveals that he was going to propose when he asks a figurine of Gollum from The Lord of the Rings what he should do with an engagement ring he had planned to give her. In the episode "The Earworm Reverberation" in season 9, Sheldon confesses his love to Amy and they get back together.

Penny

Kaley Cuoco

Penny (surname has not been revealed) (Kaley Cuoco), is Leonard and Sheldon's neighbor across the hallway. Originally from a small town outside Omaha, Nebraska, she was a waitress and occasional bartender at the local Cheesecake Factory until season 7 and is an aspiring actress. According to her friend and neighbor Sheldon, she is a "good-natured simpleton". She is kind-hearted, outgoing, and does display the most common sense out all the original 5 main characters. She also appears to be the most street-smart. Her educational qualifications (she dropped out of community college) are a constant source of disparaging comments from Sheldon. She has dated several men during the course of the series, including Kurt, Stuart, and Zack, but her recurring romantic interest is Leonard. Leonard pursued Penny during season 1; they dated briefly at the start of season 2 which led to some awkwardness; they began dating again and were a couple for most of season 3, but she broke up with him after he told Penny he loved her and she was not ready to reciprocate. Penny and Leonard begin to date again "slowly" during the fifth season, though he does upset her by impulsively asking her to marry him during intercourse at the end of season five. After several unsuccessful proposals from both sides, Penny realizes that her happiness is derived from her relationship with Leonard and they become engaged and later get married. She has a tense relationship with Sheldon, whose nerdy and obstinate personality often exasperates her, but they are ultimately good friends, helping each other out in various situations. By season four, Penny also begins to socialize more with Bernadette and Amy, who frequently hang out in Penny's apartment, go out together and comfort each other. Bernadette and Amy are both shown to be simultaneously envious of and threatened by Penny's more outgoing personality. Not much is known about Penny's family, but it is mentioned in the series that her father, Wyatt (portrayed by Keith Carradine^[7]), raised her like a boy, her mother smoked marijuana while she was pregnant with her, her sister shot her husband while they were intoxicated and her brother is a meth dealer. During her marriage to Ryan Sweeting, Cuoco was credited as Kaley Cuoco-Sweeting, starting with the season seven episode "The Convention Conundrum", but she returned to being credited as Kaley Cuoco after they separated in 2015.

Howard Wolowitz

Simon Helberg

Howard Joel^[8] Wolowitz, M.Eng (Simon Helberg) is an aerospace engineer at Caltech's Department of Applied Physics with a Master's in Engineering who often hangs out at Leonard and Sheldon's apartment. Unlike Sheldon, Leonard, and Raj, Howard has no doctorate, and often gets disparaged as a result, especially by Sheldon. He defends this by pointing out that he has a master's degree in Engineering from MIT and that the equipment he designs is launched into space, unlike the theoretical work of his friends. In the season 5 finale, Howard goes to the International Space Station on Expedition 31. Howard lives in Altadena with his domineering, belittling and unseen mother who treats him like a child. While he sometimes expresses irritation at this treatment, for the most part he appears to prefer it.^[9] Howard dotes on his mother and participates in many of her daily routines. A recurring gimmick in the series is Howard and his mother communicating with each other from different rooms by yelling, a habit which Bernadette also adopts in later episodes. His father left them when he was eleven, and Howard gets visibly distressed when the subject comes up. Howard fancies himself a ladies' man and attempts pick-up lines whenever a woman is present, which often come off as inappropriate and disgusting, although he has dropped this habit since he started going out with Bernadette. He is Jewish, but he is not very serious about his faith, and does not keep kosher. For example, when the group's favorite Chinese restaurant raised the price of pork, Howard remarked, "It's getting tougher and tougher to be a bad Jew." However, he does observe Sabbath and the Jewish holidays. In the pilot episode, it is shown that he is a polyglot and can speak English, French, Mandarin, Russian, Arabic, and Persian, along with fictional languages like Klingon and Sindarin. He is asthmatic, allergic to peanuts, almonds, and walnuts, prone to canker sores and pink eye, succumbs to seasickness, has an incredibly high genetic risk of heart illness, and has transient idiopathic arrhythmia. In season 5 episode 4, it is shown that he knows American Sign Language. Howard dated Bernadette briefly in season 3. After some difficulties, they resumed their relationship in season 4, which culminated in their engagement. In the season 5 finale, Howard and Bernadette are married on the roof of the apartment building shortly before he has to leave for Kazakhstan where he is to be sent to the International Space Station. In season 6, he finally leaves his mother's house and moves into Bernadette's apartment.^[10] In the episode "The Comic Book Store Regeneration" Howard's mother passes away in her sleep while in Florida, prompting him to move back into his home with Bernadette. Stuart, the owner of the guys' favorite comic book store, joins them, much to their annoyance.

Raj Koothrappali

Kunal Nayyar

Rajesh Ramayan^[3][11] "Raj" Koothrappali, Ph.D. (Kunal Nayyar) is Howard Wolowitz's best friend and another genius of the group; his name is usually shortened to "Raj". He is originally from New Delhi, India, and he works in the Physics department at Caltech, where his area of expertise is particle astrophysics. He lives in an apartment in Pasadena. As with his friends, he is mutually involved with and obsessed with science fiction and comic books in general, and is usually the one to propose various real-life questions derived from such works, such as the functions of the tails of the Na'vi in the film Avatar. He is also a fan of Harry Potter. Raj dislikes India, Indian food, and Indian music, he also appreciates the Indian lullabies his mother sang to him and the catchiness of Hindi phrases. Raj is a Hindu and believes in karma (reincarnation), but eats beef. Raj is very shy around women outside of his family, and during the first six seasons of the show found himself unable to speak to women or others while in the presence of them unless he drank alcoholic beverages, or he believed he had done so.^[12] When Penny, Amy and Bernadette were around, Raj usually whispered what he wants to say to Howard or Leonard, who then repeats or responds to what Raj said out loud, although at times Howard would embarrass him by saying something completely different and inappropriate.^[13] Despite this, Raj has sometimes ended up in bed with women, leaving the other guys perplexed.^[14] Unlike his friends however, Raj has many quite feminine interests such as reading Archie Comics and Twilight and watching chick flicks such as Bridget Jones's Diary. A recurring joke in the series has people, including his parents and Leonard's mother, speculating that Raj might be gay due to his feminine interests and his close friendship with Howard, with whom he has arguments similar to those of a married couple. However, Raj has always stated that he is straight, but metrosexual. He has had an infatuation with Penny, and secretly wrote love poems about Bernadette. Raj comes from a very wealthy family in India, and often communicates with his parents, Dr. and Mrs. Koothrappali, via webcam.^[12] He has a younger sister, Priya, who is mentioned to have dated Leonard briefly before the series timeline began and dates him again in season 4, breaking up with him in season 5. After making a brave speech about not being embarrassed to be single, Raj started seeing a shy and sweet woman named Lucy. Lucy has many things in common with Raj including her fear of being in large crowds. However, she feels too pressured when he asks her to meet his friends and breaks up with him. Afterwards, Raj finally speaks to Penny without having consumed alcohol.

As of season 7, he no longer requires alcohol in order to speak in front of females. In season 7, Raj starts dating Emily Sweeney, a dermatologist, and their relationship becomes exclusive at the end of the seventh season.

Additional main characters

Leslie Winkle

Sara Gilbert

Leslie Winkle, Ph.D. (Sara Gilbert) is an experimental physicist who works in the same lab as Leonard. Her first appearance was in the third episode of season one. In appearance, she is essentially Leonard's female counterpart, equipped with the black framed glasses and sweat jackets. She also happens to have a lazy eye. She is one of Sheldon's arch-enemies, due to their conflicting scientific theories. Though they both consider each other to be intellectually inferior, Leslie is much wittier than Sheldon, regularly calling him "dumbass" and besting him in their exchanges. Leslie has had casual relationships with Leonard and later Howard, considering it a completely physical reaction to her body's cycles – her voice remains emotionless even during moments of extreme physical intimacy. Leslie's final appearance was in the season 3 finale, as the writers said they did not know how to work in the character full-time.^[15] After Penny broke up with Leonard, she got intoxicated, had intercourse with him, then pushed him away. Distraught, Leonard asked for intercourse with Leslie. Leslie responded, "Let me think about it", before slamming the door on him.^[16] Gilbert and Galecki previously portrayed a couple on Roseanne,^[17] a show that was also produced by Chuck Lorre.^[15] Gilbert returns for the 200th episode of the series to attend Sheldon's birthday party, where she and Sheldon appear to have put their differences aside and become friends. After Leslie gives a speech about Sheldon and wishes him a happy birthday, she affectionately calls him "dumbass" again at Sheldon's insistence (due to his dislike for changes).^[18]

Bernadette

Melissa Rauch

Bernadette Maryann^[19] Rostenkowski-Wolowitz,^[20] Ph.D. (Melissa Rauch): is originally a waitress and coworker of Penny's at the Cheesecake Factory, which pays the way for her graduate studies in microbiology per "The Creepy Candy Coating Corollary".

She is a smart, short-tempered, ruthless and often competitive young woman who often pretends to be sweet, nice and friendly. Despite her soft, cute voice she has a darker side. A recurring joke in the series is in reference to Bernadette and her lab team handling dangerous or infectious specimens, leading to accidental by-products or exposure to diseases, in some cases resulting in Bernadette ending up in quarantine. Instances include her trying to remember whether she washed her hands while she worked with penicillin-resistant gonorrhea or creating a cold medicine that may cause acidic tears.

From Yorba Linda, California,^[21] Bernadette is of Polish origin and Catholic upbringing, and is frequently seen wearing a cross necklace. She is generally a friendly and good-natured individual, quickly making friends with Penny and Amy, as well as the rest of the gang. However, despite her short stature, she is regarded as being somewhat intimidating, largely because of her sharp tongue, aggressive demeanour and occasional signs of mania, e.g. when she got into a fight with Amy over a parking space Sheldon and Howard were fighting over, and when she explains her interest in microbiology as being because she feels like a god to the bacteria she is studying. In season 8's "The Locomotive Decoupling", Penny is interviewing for a pharmaceutical rep position with Bernadette's boss, and they both agree that Bernadette is something of a bully.

Bernadette has demonstrated that she has some influence over both her father and her husband^[22] as well as the ability to convince her father to change his mind^[23][24] without being contested and directly supervises Howard's expenditures by giving him allowance money.^[25] On one occasion, she was also able to control Sheldon, putting it down to knowing how to deal with stubborn children.^[26]

Penny first introduced Bernadette to Howard on Leonard's half-willing request. During their first date, Bernadette and Howard do not find any common field of interest until they discover that they both have domineering mothers.^[27] After their third date Bernadette declares that three dates is the threshold for deciding whether they want a long term relationship. Blindsided, Howard hesitates initially, but then impulsively proposes.^[28] Bernadette is frustrated with Howard, but when he sings a heartfelt song for her at the Cheesecake Factory, she declares that it is the most romantic thing anyone has ever done for her.^[29] A lengthy offscreen breakup occurs when she catches Howard engaging in cybersex, but Howard apologizes and she consents to restarting (as opposed to resuming) their relationship.^[30] In the season 4 finale, she obtains her doctorate and is subsequently hired by a pharmaceutical company with a high salary.^[31] While preparing for their wedding, Bernadette is shocked and repulsed when she learns about Howard's past sexual escapades, although once again, an apology and reconciliation occurs in the same episode.^[32] They marry the day before Howard leaves for his upcoming mission aboard the International Space Station.^[10] During season 6 and 7, the newlyweds deal with Howard's difficulty in readjusting to life on Earth,^[33] the struggle to keep a healthy relationship with Howard's mother,^[34] and arguments over money.^[25] In the ninth season episode, "The Valentino Submergence", Bernadette realises that she is pregnant, and eventually tells the rest of the group, comically revealing that the baby was conceived in Sheldon's bed, much to Sheldon's chagrin.

Amy Farrah Fowler

Mayim Bialik

Amy Farrah Fowler, Ph.D. (Mayim Bialik) is a neuroscientist (the same Ph.D. Bialik herself has in real life), and Sheldon's love interest in the series. She has a Ph.D. in neurobiology, with a research focus on addiction in primates and invertebrates, occasionally mentioning such experiments as getting a capuchin monkey addicted to cigarettes or starfish addicted to cocaine.

Raj and Howard found Amy through an online dating site after secretly setting up an account using Sheldon's name and information. The site matches her to Sheldon, and the two share many similar traits. Once she and Sheldon meet, she becomes, as Sheldon puts it, a girl who is his friend, but not his "girlfriend". They briefly ended their friendship when they got into an argument over whose field of study was superior.^[35] The two initially communicate via computer, but at the encouragement of the group, she starts socializing with the gang in person.

Early on, Amy is essentially a female counterpart to Sheldon. She is coldly rational, displays little emotion, is awkward in social situations ranging from endearing to embarrassing, is sometimes condescending toward those of lesser scientific knowledge. In season 5, after Amy goes out on a date with comic book store owner Stuart, Sheldon decides to solidify their relationship as boyfriend/girlfriend with a 31-page "Relationship Agreement".

In "The Launch Acceleration", Amy begins a campaign to increase Sheldon's feelings for her by becoming more involved in his interests, including video games and Star Trek, and treating him as his mother did. Sheldon says during Howard and Bernadette's wedding ceremony that he hopes the two of them are as happy together as he is alone,^[10] hurting Amy's feelings, but he spontaneously takes her hand for comfort later as Howard is launched into space.

By the beginning of season 6 they are regularly holding hands at Amy's insistence, but Sheldon repeatedly resists all of her attempts to engage in further physical intimacy. By mid-season, Sheldon gets some intimate views of Amy when he cares for her while she has the flu, pushing him further toward a traditional relationship with her. She also provides Sheldon with consoling hugs, and was slapped on the rear by an intoxicated Sheldon, telling everyone that she is a great gal.

Amy tries to move into Sheldon's apartment when Leonard temporarily vacates it, but has to give that up. Sheldon, after being prodded by Barry Kripke about his girlfriend, lies that he is having sex with Amy, though he admits to Penny that it might really happen between him and Amy and later admits it to Amy, while also engaging in Dungeons and Dragons' intercourse game play. Nevertheless, her frustration is frequently played for laughs from that point onward. In the season 7 episode "The Locomotive Manipulation", Sheldon sarcastically says he will give Amy the romance she wants, then passionately kisses her on the lips for the first time and enjoys it. In "The Prom Equivalency", Sheldon and Amy admit to being in love with each other.

While early on Amy was ambivalent and often condescending towards Penny and Bernadette, she later spends more time with them even at the expense of her time with Sheldon. As her appearances have progressed, she has shed her strident, aloof personality for a stereotypically feminine and social one, although she retains some social awkwardness. Her feelings for Sheldon have also grown considerably over time and she considers him to be ideal in almost every way, though she sometimes becomes as annoyed and frustrated by Sheldon's quirks as his other friends do.

Amy also intensely wants her relationship with Sheldon to progress to include sexual intimacy, a drastic departure from her early days as a member of her circle of friends. She has come to consider Penny a very close friend, sometimes referring to her as her "bestie", and, on another occasion, admitting her entire social life revolves around her. Penny is fond of Amy, on one occasion making an effort to salvage their friendship after she accidentally hurts Amy's feelings. To her dismay, however, Amy often fails to grasp the concept of "girl talk", by talking about feminine hygiene and anatomy when in her presence and at times being brutally honest.

Amy often demonstrates an infatuation towards Penny, and occasionally Bernadette, to whom she is somewhat condescending, though still considering her a close friend. These including making inappropriate comments about Penny's body and Bernadette's personality. After attending a science convention with Bernadette in "The Hofstadter Insufficiency", Bernadette and Amy found common interests and became better friends.

When she feels that Leonard is interested in her, she admits to Penny that she has a better shot getting her into bed than Leonard. In episode 8 of the fifth season, she suggests that Bernadette's bridal shower should consist of naked bridesmaids washing each other, and she proposes that the bachelorette party consist of a Native American sweat lodge and women dancing around painting fertility symbols on the bride's naked body. Her more arrogant side is shown in "The Pulled Groin Extrapolation", where she is convinced that Leonard has fallen for her after he accompanies her to a friend's wedding and gives her a chaste kiss on the cheek, even though he has no such feelings.

In "The Benefactor Factor", it is revealed that she is technically engaged to Saudi Arabian Prince Faisal who resides in Riyadh, who is the source of much of her lab's funding. Amy can also play the harp. In "The Scavenger Vortex", it is suggested that she attended Harvard University. In the final episode of season 8, "The Commitment Determination", Amy decides to take a break from her relationship with Sheldon due to the lack of physical affection. It is then shown that Sheldon intended to propose to Amy, but she took a break from the relationship before he could ask her. Amy ultimately breaks up with Sheldon after a serious falling out, but they slowly rekindle their relationship and eventually have sex as a birthday present from Sheldon. Amy later prepares a surprise birthday party for Sheldon, and invites Adam West to make him happy in response to a rude joke once played on Sheldon by his sister and her friends about Batman attending his birthday.

Stuart Bloom

Stuart David Bloom^[36][37][38] (Kevin Sussman): Stuart runs The Comic Center of Pasadena, the comic book store that the guys patronize. Stuart is characterized by his low self-esteem and loneliness, which result in pathetic attempts to engage with women and win favor with the main cast. This is despite owning his own (albeit troubled) business, and being a talented portraiture artist who attended the Rhode Island School of Design.

During Stuart's first appearance, the guys brought Penny to the store and he managed to ask her on a date. The date went fine until Stuart was dragged into discussing comic books by Sheldon, leaving Penny bored.^[39] On a second date with Penny, Stuart asked for Leonard's advice, but feeling threatened, Leonard ultimately gave him bad advice. The date went fine, but when Penny was getting romantic with Stuart she mistakenly called him "Leonard", leaving him devastated.^[40] He also briefly went on a date with Amy in season 5; although Sheldon interrupted the date to solidify his relationship with Amy.

Stuart was the partner of Wil Wheaton in a trading card game tournament in which they defeated the team of Raj and Sheldon.^[27] As Stuart runs a comic book store, he has an almost encyclopedic knowledge of comic books and superheroes. In the season 4 episode "The Toast Derivation", he mentions that he is in financial trouble and that the comic book store is now also his home. In "The Justice League Recombination", he states that he works 70 hours and clears an average of $1.65 per hour after expenses, so his income per week would be $115.50. At Howard's bachelor party during the "The Stag Convergence" episode, Stuart uses his toasting turn to tell Howard how lucky he is by contrast to Stuart's own existence. In the season 6 episode "The Bakersfield Expedition", Penny asks Stuart for advice about comics, and he sullenly answers, "Don't own a store that sells them".^[41]

During "The Decoupling Fluctuation", Stuart becomes close friends with Raj and starts hanging out with the gang as a replacement for Howard while Howard is in space. Before accepting this, Sheldon quizzes Stuart as to where he went to school (Stuart has an art degree). Sheldon concedes to adding Stuart to the group, calling him "fake-Wolowitz" and equating his past career choice in art to Howard's as an aerospace engineer as "equally ridiculous". When Howard returns from space Sheldon wants to dismiss Stuart from the group but Raj objects. Leonard tie-breaks on the basis that they are receiving a 20% discount in Stuart's store. Sheldon relents after Stuart offers to go as high as 30%. Initially, Sheldon had stipulated that Stuart must act like Howard while in the gang's presence. After his comic book store burns down Howard offers him a place to stay and a job as his mother's nurse. At the time all other nurses have been driven away but Stuart likes the job and develops a surprising closeness with Howard's mother, even staying there long after she had recovered, much to Howard's annoyance.^[42]

After the death of Howard's mother, Howard and Bernadette move back into the house, with Stuart still staying. In the season eight finale, the two attempt to ask Stuart to move out, but are unable to bring themselves to do it after learning it is his birthday. As of the start of the ninth season, he still lives there. He moved out later that season.

Emily Sweeney

Emily Sweeney, MD (Laura Spencer):^[43] A dermatologist at Huntington Hospital who Raj finds on an online dating site. Emily went to Harvard, and is shown to have a slightly alarming personality; she is shown to delight in the macabre when she states that she likes her job because she can cut things with knives, and likes Sally from The Nightmare Before Christmas (of whom she has a tattoo on her shoulder) because she has lots of scars and her limbs had to be sewn back on.

In season 7, after finding Emily's online dating profile, Raj has Amy contact her as his wingman instead. Amy and Emily exchange emails and find they have a lot in common. Emily doesn't like Raj's inability to correspond with her directly, and when Amy and Emily meet to have coffee, Raj barges in to show that he is not a passive guy. Emily calls him a "weird guy with no boundaries" and leaves, ditching Amy for their next get together in the process. Raj later bumps into Emily in "The Indecision Amalgamation" and apologizes for their previous encounter. She gives him another chance and agrees to go out to dinner with him, where he tells her that his ex-girlfriend Lucy wants to see him again, although this does not bother Emily. In "The Relationship Diremption", Raj and Emily have dinner with Howard and Bernadette. Upon meeting Emily, Howard recognizes her from a blind date they had sometime before he met Bernadette. He had a sick stomach, had to use the bathroom, and clogged the toilet. Since he was too embarrassed to tell her, he escaped through the bathroom window. Emily reveals that she and her friends refer to Howard as "Clogzilla". In "The Gorilla Dissolution", Raj and Sheldon bump into Emily at the movies with another guy. Later, she visits him to talk and reveals that the guy was her tattoo artist who had been asking her out for weeks and she did so just to end the obligation. Emily then spends the night and in the next episode, Raj reveals to the gang that he and Emily are exclusive.

In season 8, Raj introduces Emily to Leonard and Penny, however Penny senses that Emily does not like her. Emily reveals that she is uncomfortable with the fact that Raj and Penny previously hooked up. Emily and Penny later sit down to settle their differences; however, after the meeting both women state that they hate one another. Emily continues to socialize with the gang by attending the prom that Amy and Bernadette organize for the gang and going to an "escape room" with Raj, Leonard and Amy. In "The Colonization Application", Raj gets into trouble with Emily when he snoops around her apartment while she is at work and breaks her drawers, although she gets her revenge by tricking Raj into thinking there is something morbid in her closet. In "The Commitment Determination", Emily suggests to Raj that they have sex in a graveyard. Raj wonders whether he should break up with Emily due to her alarming personality. On the date, Raj tries to break up with Emily but instead tells her that he loves her.

In season 9, Raj somewhat rashly breaks up with Emily after meeting another girl, Claire, and fantasising about starting a family with her, though Claire makes amends with her boyfriend and berates Raj for his actions. He tries to reconcile with Emily, but she shuts the door in his face. Later in the season Emily and Raj reconcile after a tearful phone call and gift from Emily.

Recurring characters

The following list is sorted in alphabetic order of first names.

Alex Jensen

Margo Harshman

Alex Jensen (Margo Harshman): An attractive Caltech graduate student who appears in season six. She is hired by Sheldon to review his kindergarten and elementary school notebooks for any possible Nobel Prize winning research and attend to the tasks that Sheldon perceives a waste of his own valuable time. Amy is at first jealous until she sees Alex instead flirting with an unresponsive Leonard.

After repeated flirts by Alex, Leonard finally realizes that Alex is making advances toward him. While proclaiming his loyalty to Penny, Leonard is flattered. Sheldon interferes (with the perceived intention of mitigating a situation that needed none) by lecturing Alex, but only succeeds in insulting her. After Alex files a sexual harassment complaint, Sheldon is forced to apologize and is ordered take a university-mandated online sexual harassment course. Because Sheldon considers his own time is too valuable to waste on it, Sheldon asks Alex to take the course instead.^[44]

Arthur Jeffries

Bob Newhart

Arthur Jeffries, aka Professor Proton (Bob Newhart) is the star of a science show that Sheldon and Leonard watched as children. After the show was cancelled, Jeffries was not taken seriously as a scientist and resorted to doing children's parties as his persona. In "The Proton Resurgence", Sheldon hires him to do a private party for Leonard and himself (and Penny). Later, Jeffries ends up having a heart attack as a result of climbing the apartment stairs with his equipment. He asks Sheldon to take his place at a party for a Korean family, which Sheldon agrees to do as "Professor Proton, Jr".

While Sheldon idolizes him, Jeffries is constantly irritated by Sheldon's personality, and takes a shine to Penny. In "The Proton Displacement", Leonard, Sheldon, and Amy bump into Jeffries at a drugstore, and Sheldon becomes upset when Jeffries asks Leonard for help on a paper instead of him, and when he finds out that Jeffries thinks he is annoying, Sheldon works with Bill Nye the Science Guy, whom Jeffries accuses of stealing material from his TV show. After Nye abandons Sheldon and files for a restraining order against him, Jeffries arrives at Sheldon and Leonard's apartment and asks Sheldon for his advice on his paper (although Sheldon already hacked his email account and read it for himself).

In "The Proton Transmogrification" on Star Wars Day, Leonard tells Sheldon that Jeffries has died. Sheldon immediately pretends like he does not care and refuses to go to the funeral. Jeffries appears to Sheldon in a dream, where Sheldon compares him to Obi-Wan Kenobi, dressing him in Jedi robes and making him appear as a Force ghost. When Sheldon asks for his wisdom, Jeffries tells Sheldon to appreciate everything in life, including his friends, and never take it for granted.

Jeffries returns in "The Opening Night Excitation" when his ghost convinces Sheldon to spend time with Amy on her birthday instead of going to see Star Wars: The Force Awakens as he had planned to do for months. After hearing Professor Proton's words, Sheldon decides to prove his devotion to Amy by finally having sex with her, as she has been hoping he will do so for the past few years. Some time later, after Sheldon takes Amy to see The Force Awakens, Jeffries returns to Sheldon to ask him about his first sexual experience with her, but Sheldon thinks Jeffries is talking about the film and tells him he enjoyed it.

For his role as Jeffries, in 2013, Newhart won his first Primetime Emmy Award.

Barry Kripke

Barry Kripke, Ph.D. (John Ross Bowie): A co-worker of the guys who frequently clashes with Sheldon. He works in plasma physics. Kripke has a case of rhotacism in which he pronounces the letters "R" and "L" as "W" in much the same way as Elmer Fudd from Looney Tunes and Gilda Radner in her "Baba Wawa" sketches. In season 5, Kripke purchases an iPhone with voice recognition technology, but due to his rhotacism, the device is incapable of understanding his verbal "wequests", prompting him to deride it as ineffective. Until season 7, it was never clarified if he was aware of his impediment.

In his first appearance he pits his robot, the Kripke Krippler, against the men's robot, M.O.N.T.E., in an unofficial robot fight.^[45] The guys lose to Kripke, and M.O.N.T.E. is destroyed. In "The Friendship Algorithm", Sheldon attempts to befriend Kripke in order to gain access to an open science grid computer to carry out research, but it turns out to be futile, as Kripke has no control over the computer's usage time, and Sheldon consequently expels Kripke from the group.^[46] Kripke continues his antagonism towards Sheldon in "The Vengeance Formulation" by pulling a prank on Sheldon when he is a guest on NPR's Science Friday by putting a helium tank in his office.^[28] In "The Toast Derivation", Sheldon tries to befriend Kripke and a few others when he is feeling excluded by his friends, but Kripke and the others all connect in a manner that Sheldon finds 'wrong' and leaves.^[47]

In season 5, Kripke and Sheldon battle over a retired professor's office, however after a long sports contest, Kripke loses to Sheldon. He is later invited to Howard's bachelor party, where he uses his turn toasting to complain that there are no strippers at the party.

In season 6, Kripke and Sheldon are forced to work together on a proposal involving fusion reactors, which involves an exchange of work. Sheldon is shocked to discover that Kripke's work is more advanced than his own, and he tearfully admits as much to Amy. Kripke assumes that Sheldon is in a sexual relationship with Amy, and that has led to his work quality declining, and Sheldon does not deny it (although this appears to be just a convenient excuse since his work is inferior to Kripke's). Kripke also battles for Tenure alongside Sheldon, Leonard and Raj.

In season 7, Kripke ridicules Sheldon when his discovery of a new element was false, nicknaming Sheldon "The Retractor".

In season 9, Kripke calls Sheldon and Amy's live show of Fun with Flags along with Raj and directs the conversation to irrelevant questions to the show. He also uses the show to call out for potential romantic relationships and asked Amy questions about her lovelife when she and Sheldon broke up.

Beverly Hofstadter

Christine Baranski

Dr. Beverly Hofstadter (Christine Baranski): Leonard's overly analytical mother. Beverly is a neuroscientist as well as a psychiatrist. She is Sheldon's female equivalent regarding neurotically strict speech patterns, lack of social conventions, and attention to detail. Beverly mentions that Leonard's brother and sister are more successful in their respective fields than he is. One of her famous books is "Needy Baby, Greedy Baby", in which she describes an infant's (aka Leonard's) unrealistic nurturing expectations. Sheldon often refers to her books when frustrated with Leonard's attempt to obtain some of his personal needs in their relationship. Leonard sees his mother as cold and un-nurturing, even telling Penny that one time he made a hugging machine just to get hugs (and that his father asked to borrow it). The lack of Beverly's maternal feelings and actions toward Leonard have led to him being called the "King of Foreplay" because of his obsessive need to please.

In her first visit, Beverly makes Penny cry by delving into her history with her father (driving her and later Leonard to the bottle), and considers Raj and Howard's relationship to be an "ersatz homosexual marriage". After bonding with Sheldon, Beverly sings Journey's "Any Way You Want It" with him on karaoke. In season 3, Beverly comes to visit at Christmas, where she later gets drunk with Penny at The Cheesecake Factory, gropes a busboy and then goes to Del Taco and returns to Leonard and Sheldon's apartment where she kisses Sheldon whilst intoxicated.

In season 5, Sheldon calls Beverly on Skype to help Leonard following Penny and Raj's hook-up, and she tells Leonard to "buck up, sissypants...If you need any more help from me my books are available on Amazon".

In season 7, Leonard uses Beverly's latest book to get sympathy from Penny, however Bernadette finds out from Howard what Leonard is doing and tells Penny, who calls Beverly, leaving a pants-less Leonard to chat with his mother on Skype. Leonard later informs his mother of his engagement to Penny, however she reveals that Sheldon already told her. She decides to accept his relationship with Penny because Sheldon likes her.

In season 8, Beverly comes to visit to see Leonard receive an award, where she meets Sheldon's mother, Mary. The mothers get into an argument after Beverly describes Mary's religious beliefs as a superstition and Mary in turn berated Beverly for her cold and distant attitude towards Leonard. Beverly later reflects with Sheldon that perhaps there are other ways to raise children than she did. The mothers make up and Beverly tries to show affection by hugging Leonard, though it is awkward for both of them.

For her role as Beverly, in both 2009 and 2010, Baranski was nominated for an Emmy Award for Outstanding Guest Actress in a Comedy Series.

Claire

Claire (Alessandra Torresani), a writer for a children's science fiction series who Raj and Howard meet in the comic book store. Claire wants to collaborate with Raj on the science portions of a movie script. She is only interested in his help while Raj has visions of marriage and children. After Raj breaks up with Emily, he calls Claire on Valentine's Day; however, she just got back together with her boyfriend. She also calls Raj an 'ass' for breaking up with Emily just before Valentine's Day, although later she asks Raj out for a drink when she again breaks up with her boyfriend.

Dave Gibbs

Stephen Merchant

Dave Gibbs (Stephen Merchant): A tall British man who dates Amy after she breaks up with Sheldon. Dave is recently divorced because his wife left him for a French chef. When her friends try to find Amy a date on a dating Mobile app, they see a text message from Dave, and Amy reveals they have already gone out together for coffee. Sheldon is about to propose to Amy for closure when he sees Amy and Dave share a kiss after their date. When Amy and Dave later go out again for dinner (while Penny, Bernadette, and a reluctant Leonard spy on them), he shows an unusual fascination with Sheldon, which discomforts Amy. He considers Sheldon and Leonard to be physics superstars and idolizes them. He later gets an opportunity to meet Leonard and shake his hand after Leonard has to relieve himself whilst spying on their date, and with great excitement, Dave announces that he will never again wash his hand. After Sheldon rejects Amy's proposal that they be a couple again, Amy once again tries dinner with Dave, who goes out of his way to refrain from mentioning Sheldon, knowing how uncomfortable that subject made her previously. Sheldon then suddenly arrives and professes his love to Amy, and the two mend their relationship, leaving Dave to awkwardly excuse himself and invite Sheldon to meet again on his way out.

Dr. Eric Gablehauser

Dr. Eric Gablehauser (Mark Harelik): The head of the Physics Department, Dr. Gablehauser is the group's boss at the university. When he first starts working at the university, he fires Sheldon after Sheldon insults his intelligence. Eventually, Sheldon is rehired because Gablehauser became romantically interested in Sheldon's mother. Gablehauser later hosts the Physics Bowl.,^[48] and gives Raj attention when he is featured in a People Magazine article for discovering a planet.

Dr. V.M. Koothrappali

Brian George

Dr. V.M. Koothrappali (Brian George): Raj's father in India. He and his wife communicate with their son via Skype and constantly try to arrange dates for him. They want their son to marry a woman of Indian descent, and give them grandchildren.^[12] Although in many episodes Raj mentions that he grew up in poverty, his friends remind him of the contrary by pointing out that Dr. Koothrappali is a gynaecologist, drives a Bentley, and employs servants.^[49] In one such episode, Raj replies that the Bentley is leased and there are only four servants in his family home, two of whom are children. Dr. Koothrappali enjoys Doogie Howser reruns, which are apparently new to India.^[12][49] Other than Raj, he also maintains contact with their daughter Priya via Skype whenever she is out of India. In season 4, Dr. Koothrappali becomes angry with Leonard when he learns that his daughter, Priya, is dating Leonard without his knowledge. According to Sheldon, the Koothrappalis are "Richie Rich rich".

The Koothrappalis go through a rough patch in their marriage, culminating in them separating in season 8 around the time of their 40th wedding anniversary, with Dr. Koothrappali moving out and Mrs. Koothrappali setting fire to his car. Dr. Koothrappali makes his first physical appearance on the show in season 8, visiting the main characters at a Christmas party after the divorce. Dr. Koothrappali later cuts off Raj financially when he buys a helicopter drone, but Raj manages to turn the situation around by pitting his father against his mother.

Mrs. Koothrappali

Alice Amter

Mrs. Koothrappali (Alice Amter): Raj's mother in India. She and her husband communicate with their son via Skype and constantly try to arrange dates for him. They want their son to marry a woman of Indian descent, and give them grandchildren.^[12] Mrs. Koothrappali is especially worried that, despite Raj being old enough to marry, the closest they have to a daughter-in-law is "that little Jewish boy Howard".^[50] She enjoys Doogie Howser reruns, which are apparently new to India.^[12][49] Other than Raj, she also maintains contact with Priya via video chat whenever she is out of India. She previously had some anger towards Leonard when it became apparent that he was dating Priya without her knowledge.

Following their divorce in season 8, Raj mentions that his mother bought the book Eat Pray Love and used it to set fire to her ex-husband's car. Mrs. Koothrappali makes her first physical appearance on the show in "The Graduation Transmission", where Raj uses the Koothrappali's divorce to get money from her when his father cuts him off financially, and pits her against her ex-husband.

Janine Davis

Regina King

Janine Davis (Regina King): A human resources representative working at the university. In season 6, after Sheldon offends his assistant Alex whilst trying to solve a problem regarding her crush on Leonard, Mrs. Davis is left to handle a sexual harassment complaint against Sheldon by Alex. Sheldon tells Mrs. Davis she is a "slave" to her "sexual urges" and in his attempt at defense, rats out "worse behavior" by Raj, Howard, and Leonard, prompting Mrs. Davis to summon them to her office as well. Mrs. Davis later serves on the tenure committee that is considering Raj, Sheldon, Leonard and Kripke for a vacant tenured position, causing each of them to try to "butter up" Mrs. Davis. Sheldon, in an attempt to win her over, yet again offends her by giving her the boxset for the TV series "Roots", and when she asks Sheldon why he thought this would be an appropriate gift Sheldon asks "you are black, right?". Despite this, Sheldon is still short-listed for Tenure, however he offends Mrs. Davis yet again by giving her what he considers a traditional "black" handshake.

In season 7, Mrs. Davis is revealed to be recently divorced after her husband cheats on her, and Raj attempts to strike up a conversation with her at a university mixer. After offending her, Raj apologizes and the two talk about their troubles. While Raj is insistent that the two of them had a "moment", Howard disagrees.

Kurt

Kurt (Brian Patrick Wade): A tall, intimidating bodybuilder, Kurt is Penny's ex-boyfriend at the beginning of the series. In the pilot, Penny reveals that he cheated on her and Leonard and Sheldon later go to his apartment and attempt to retrieve Penny's television set from him, however they were unsuccessful and Kurt apparently found them so irritating that they returned home without pants.^[51] Kurt is invited to Penny's Halloween party, for which he dresses up as a caveman, where he has yet another run in with Leonard, who is dressed as a hobbit. After seeing Penny kissing Leonard, Leonard victoriously shouts to him "That's right, you saw what you saw. That's how we roll in The Shire!"^[52]

In season 2, Penny experiences financial difficulties. After Leonard learns about Penny's problems, he tries to help her cut expenses, and in the process learns that Kurt owes her $1800. Without telling Penny, Leonard and the guys go to Kurt's place to collect the money, but they are unsuccessful, and Kurt writes "I owe Penny $1800 ~ Kurt" on Leonard's forehead in indelible ink. Later, Penny reveals that Kurt visited her the next morning and paid her in turn. However, much to Leonard's disappointment, Kurt never told Penny about Leonard's visit, and instead took the opportunity to ask Penny out for dinner.^[53]

Lucy

Kate Micucci

Lucy (Kate Micucci): A woman who shows up at a party at the comic book store on Valentine's Day for people who had no dates. She has social anxiety issues, which allows her and Raj to connect. On their first date, she becomes so nervous that she goes to the bathroom and climbs out of the window to get away. Raj falls apart and refuses to leave his apartment; however after apologizing to him, Lucy and Raj start afresh. Raj and Lucy have a date at a library and communicate via text messages and, at the end, she offers to kiss him, but chickens out at the last second. In "The Bon Voyage Reaction", Raj tries to introduce Lucy to the rest of the gang. Lucy becomes nervous at the thought of meeting so many new people that Raj suggests she meet just one of his friends first, to which she agrees. Lucy meets Amy, however Raj pressures Lucy and upsets her. Lucy breaks up with Raj via an email, and afterwards a heartbroken Raj finally speaks to Penny without having consumed alcohol.

In season 7, Penny meets Lucy at The Cheesecake Factory and confronts her about her breakup with Raj, and later Lucy arranges to meet with Raj to apologize to him for breaking up with him via email. This leads Raj to believe the two of them will get back together, however Lucy tells him she is with someone else. Lucy is later mentioned in "The Indecision Amalgamation". Raj gets a message from her about getting back together; however after finding out that he is also dating Emily, Lucy rebuffs Raj.

Mary Cooper

Laurie Metcalf

Mary Cooper (Laurie Metcalf): A devout Christian from Texas, Mary is Sheldon's mother. She has two other children besides Sheldon; Sheldon's twin sister, Missy, and his brother George, who is shown via a family tree to be three years older than Sheldon and Missy. Her husband, a rambunctious alcoholic, was also named George, but he died when Sheldon was still a boy. To Mary's relief, her other children do not share Sheldon's hyper-intelligence, once commenting to Leonard "I thank the good Lord my other kids are as dumb as soup". Mary herself is not intellectual but is quite wise, though she is prone to making insensitive comments such as calling Japanese words "kung fu letters" at a sushi restaurant, or calling Native Americans "our Indians". Despite her extreme religious views, she is tolerant of other faiths, as evidenced by her serving Raj a dish of chicken after making sure it was not something Indians considered "magical". She also struggles to follow her beliefs sometimes. She is a loving mother and has been able to control Sheldon, with Leonard describing her as Sheldon's "Kryptonite" to Penny. When Penny and Sheldon engaged in a fierce dispute, Penny called for Mary's help, who subsequently called and scolded Sheldon about his actions.^[54] Leonard wishes his mother was as loving as Sheldon's mother, although Sheldon himself appears at best ambivalent about her parenting. It is once mentioned by Sheldon that Mary once hit him with a Bible because he refused to eat his Brussels sprouts. She apparently thought something was wrong with her son while he was growing up, as Sheldon will often remark after someone calls him crazy, "I'm not crazy; my mother had me tested!" Though Mary confirms this, she wishes that she had taken him to Houston for further testing.

In her first visit, Leonard calls Mary to intervene when Sheldon is fired for being disrespectful to his new boss, Dr. Gablehauser. She manages to convince Sheldon to apologize and he gets his job back, and she becomes romantically interested in him. When Sheldon asks "Is Dr. Gablehauser going to be my new daddy?" Mary replies "We'll see".

In season 3, after returning from the North Pole, Sheldon returns to his home in Texas after the other guys tampered with his research. Mary calls the guys and they come to fetch Sheldon. Sheldon initially refuses to leave although after an argument with his mother about evolution, Sheldon decides to leave. Mary is again called to intervene in "The Zazzy Substitution" when Sheldon buys a clowder of cats after his "break-up" with Amy. Mary uses reverse psychology to get Sheldon to reconcile with Amy. She again comes to visit in "The Rhinitis Revelation" before going on a Christian cruise, and Sheldon becomes jealous when she would rather go sightseeing with the rest of the gang instead of cooking for him and attending physics lectures.

In season 7, Sheldon returns to Texas to assist Mary in the birth of his twin sister's baby. Howard later takes Sheldon to see Mary after visiting NASA headquarters, but flees after Sheldon sees her having sex. Sheldon returns and gets into an argument, and is sent to his room. After Howard tells him about how he drove away an admirer of his mother, Sheldon apologizes to Mary, saying that he will accept her choices on the outside while condemning her internally for being a hypocrite by going against her religious beliefs. Mary forgives him.

In season 8, Mary meets Leonard's mother Beverly, and they get into an argument when Beverly offends Mary by criticizing Mary's religious beliefs, and Mary in return berates Beverly for her cold and distant attitude towards Leonard.

Mike Rostenkowski

Mike Rostenkowski (Casey Sander), a tough, retired police officer and Bernadette's father. Mike has a rough and rude personality and often bullies others, although he deeply loves his daughter, calling Bernadette his "little girl". Before he is first seen, Bernadette establishes his personality by telling Howard a long list of subjects he cannot discuss with Mike, including Jimmy Carter, foreigners, homosexuals, and even Howard's Jewish identity.

In his first appearance, he tells Howard that, while he does not think highly of him, his respect for Howard grew when he learned he had been selected to become an astronaut. However, after Howard expresses his fears about not returning from space, Mike believes Bernadette will have no trouble finding another suitable bachelor if Howard dies in space, much to the future astronaut's dismay. In the season 5 finale, Mike attends Howard and Bernadette's wedding and walks his daughter down the aisle.

In season 6, Howard and Mike are pushed into a fishing weekend by their spouses, but neither man really wants to go. Mike suggests that they go to a casino to shoot craps. Having earned more of Mike's respect, Howard is now able to address him as "Mike" rather than "Sir".

In season 7, because his wife is out of town, Bernadette gets Mike to come to Howard's mother's house for Thanksgiving dinner, though he would rather watch football at home. Since Sheldon understands football from growing up with his father, Mike and Sheldon bond and drink heavily together. After insulting Howard, Mike later tells Howard that he isn't "all that bad" but implies that this statement is untrue when he comments on his drunken state. In "The Table Polarization", Mike, Bernadette, Raj, and Mike Massimino (via Skype) perform an intervention on Howard's decision to go back to space. Mike mentions that Howard asked him to shoot him in the foot to avoid the first space mission, which Howard insists was a joke.

President Siebert

Joshua Malina

President Siebert (Joshua Malina): The president of the California Institute of Technology; he is married and has a teenage daughter. Siebert is often mentioned by Sheldon. A recurring gag is that Sheldon often calls or visits Siebert in the middle of the night to get information, and Sheldon usually gets a bitter response. Siebert sends Sheldon on the expedition to the North Pole at the end of season 2.

In his first appearance, Siebert organizes a get-together with wealthy donors and faculty members in order to garner funds for the university's programs. He urges the guys to make an appearance to schmooze the donors so that they will give to their projects. Seeing Sheldon's behaviour toward the donors, he asks that he not appear again.

In season 5, Siebert forces Sheldon to use up his vacation days, and when Sheldon and Kripke battle for an office at the university, they interrupt Siebert at a urinal to get him to make a decision on who gets the office.

Priya Koothrappali

Priya Koothrappali (Aarti Mann): Raj's younger sister. Having graduated at the top of her class at Cambridge University (where like Leonard, her roommate was from Texas), she is one of the lead attorneys at India's biggest car company.

In her first appearance Priya has a two-day layover and comes to visit her brother. It is revealed that she and Leonard had a relationship five years earlier (without her parents' or Raj's knowledge) when she was in town, and that Leonard had been much more invested in the relationship than she was. Leonard even offered to relocate to New Delhi to be with her. He tries to keep their relationship a secret from the guys, but Sheldon discovers Priya in their apartment after spending the night together. Leonard eventually reveals to the rest of the guys that he spent the night with Priya, as he is unable to bear the burden of keeping the secret.^[55] Priya returns to Los Angeles for business in "The Cohabitation Formulation" and she and Leonard decide to try and have a real relationship, over the protests of Raj. It upsets Raj to know that his sister is having sex with one of his best friends (sometimes in Raj's bed). Priya soon becomes jealous of Penny and asks Leonard to stop spending time with her, which causes Penny, Amy and Bernadette to dislike her. Priya contests Sheldon's roommate agreement with Leonard, employing her legal background to deny Sheldon power over Leonard, but Sheldon drafts a new agreement. and blackmails Leonard into signing it by threatening to tell Priya's parents she is dating Leonard, which she cannot bear because they want her to date an Indian (although her father would accept her dating Howard due to his belief that Jews are financially savvy and do not drink much). At the end of season 4, it is revealed she is moving back to India and has not told Leonard, which Leonard interprets as the end of their relationship, leading him to expose their secret relationship to her parents.

In season 5, although they are separated, with Priya moving back a month earlier than expected, they nonetheless remain in-touch via Skype, having a cyber-dinner date/breakfast date. At Howard's suggestion, Leonard and Priya also attempt to simulate intercourse, but when it comes time for her to remove her clothing, Leonard's screen freezes up because of exceeding the bandwidth. Leonard later manages to get cue cards to help himself with a seduction speech to Priya, but while delivering it to her, he inadvertently reveals to her parents that they are cyber-dating (they were in the same room as she when he called), with them acidly asking for him to continue with the speech.^[56] In "The Good Guy Fluctiation", Leonard tells Priya about his attraction to a comic book enthusiast named Alice, Priya admits to cheating on him with her former boyfriend, which visibly upsets Leonard. When Priya states that they both messed up a little, Leonard retorts that while he messed up a little, she messed up a lot.^[57] She claims that it is not a competition, to which he replies that it is and that she won and he switches off his laptop. In the next episode, Leonard refers to himself as single, indicating that he and Priya have broken up as a result of their last conversation.

Stephanie Barnett

Sara Rue

Stephanie Barnett, MD (Sara Rue): A doctor and highly distinguished surgical resident at Fremont Memorial. She did her medical internship at Lawrence Memorial in Galveston, Texas, which is where Sheldon was born.^[58]

Stephanie is picked up in a bar by Howard but when his plan to let her drive the Mars rover fails, she leaves Howard's office with Leonard and the two immediately show an attraction to each other.^[59] Howard becomes angry when he finds out, however he soon changes his mind when Stephanie sets Howard up with one of her friends. Sheldon begins meddling in Stephanie and Leonard's new relationship in an effort to strengthen it, since in his eyes, Stephanie is the only "tolerable" mate Leonard has had.^[58] After several weeks of dating, Stephanie officially begins living with Leonard in his and Sheldon's apartment (although Leonard does not realize this until Sheldon and Penny point it out to him). Stephanie uses sex to manipulate Leonard when he tries to slow down the relationship. After much hesitation, Leonard texts her at the university and tells her to move out because he is uncomfortable with the pace of the relationship, although it is implied he leaves to have sex with her. They are not seen breaking up on camera and she is neither seen or mentioned again.^[60]

Series co-creator Bill Prady said of the relationship: "Stephanie was a chance for Leonard to learn that just because someone loves you, doesn't mean you'll love them back".^[61]

Wil Wheaton

Wil Wheaton, who plays a fictionalized version of himself

Wil Wheaton (a fictionalized version of himself): Wesley Crusher in Star Trek: The Next Generation, whom Sheldon idolized as a child, and became a "mortal enemy" of his after an incident that occurred in 1995 when Sheldon was devastated because Wheaton failed to show up at a fan convention that Sheldon took a 10-hour bus ride to attend.

In season 3, Sheldon enters a trading card game tournament (Mystic Warlords of Ka'a) to confront Wheaton. When Sheldon is about to defeat his hated rival, Wheaton tells him that he missed the 1995 "Dixie Trek" convention because his grandmother had died. In sympathy, Sheldon deliberately messes up his next move in order to benefit Wheaton. Wheaton reveals that he lied about his grandmother and then wins the game by taking advantage of the opening Sheldon leaves him. Wheaton later plays in a bowling match against Sheldon, where he uses gamesmanship again, breaking up Leonard and Penny in order to win.

In season 4, Wheaton appears at a special screening of Raiders of the Lost Ark and uses his celebrity status to go to the front of a long line. This antagonizes Sheldon, who derides him as the "Jar Jar Binks of the Star Trek universe". Wheaton and his entourage effectively prevent Sheldon and his friends from attending the screening when the last seat in the theater goes to the person directly in front of them in line. Ultimately, Sheldon steals the reels containing the prints of the film and Wheaton leads a mob of angry audience members after Sheldon.

In season 5, Wheaton invites the guys to a party at his house and appears to be genuinely sorry for his past actions, giving Sheldon a signed Wesley Crusher action figure as a way of thanking Sheldon for being a fan. His gesture is met with a renunciation of his "mortal enemy" status and a hug from Sheldon. Wheaton is invited to Howard's bachelor party, where he films the toasts and uploads it to the Internet, getting Howard and Raj in trouble with Bernadette.

In season 6, Wheaton appears in a Star Trek-themed episode of Sheldon's web-series Fun with Flags and insults Amy after she criticizes his performance. After Sheldon ditches Amy to spend time with Wheaton, Amy becomes angry with Sheldon, who later unknowingly becomes intoxicated and almost start a fist fight with Wheaton, demanding an apology.

In season 7, Amy calls Wheaton to cheer up Sheldon after Leonard disproves Sheldon's scientific discovery. Wheaton later gives Penny advice when she wrestles with whether to take a role in the sequel to a low-budget horror film in which she once starred. After taking the role, Penny finds that Wheaton is also appearing in the film. Wheaton and Penny are both fired from the film after an argument with the director.

In season 8, Wheaton invites Penny to appear on his podcast, where she talks about her acting career. Leonard and Penny get into an argument on air, much to the amusement of Wheaton.

In season 9, Wheaton introduces Adam Nimoy, son of Mr. Spock portrayer Leonard Nimoy, to Sheldon, for Sheldon to be interviewed for a documentary that Adam Nimoy is producing about Spock and his impact on popular culture. In a later episode, Wheaton fills in for Sheldon when he joins Leonard, Howard, and Raj for the midnight premiere of Star Wars: The Force Awakens. When he arrives at the theater, the audience immediately jeers him for dressing as Spock, but Wheaton explains that he did so intentionally because he believes the audience should not take whether the film succeeds or fails so seriously. He appears again to celebrate Sheldon's birthday in the show's 200th episode, "The Celebration Experimentation".

Wheaton, LeVar Burton, Leonard Nimoy, Brent Spiner and George Takei have all appeared on the show, making the Star Trek franchise the most represented franchise on the show in terms of guest appearances.

Mrs. Wolowitz

Mrs. Debbie^[62] Wolowitz (voiced by Carol Ann Susi) is Howard's over-protective, controlling, belittling, but loving and caring stereotypical Jewish mother. The character is not shown on-screen with the exception of one episode in season 6 in which her body, but not face is briefly shown. Mrs. Wolowitz's raspy voice is heard usually in scenes at her house, which she shares with Howard. She talks to Howard always by yelling at him from another room, which results in awkward conversations with Howard yelling back at her. In a flashback, when the guys hear her yelling in a masculine voice, they ask Howard if that was his father, to which Howard replies "If she grows any more hair on her face, yes".

Mrs. Wolowitz is also described as being enormously obese and wearing a wig and painted-on eyebrows. Mrs. Wolowitz seems to be oblivious to Howard's work as an engineer and treats him as though he is still a child. She frequently refers to Leonard, Sheldon, and Raj as Howard's "little friends" (as in, "I made some cookies and Hawaiian Punch for you and your little friends!") and often refers to Caltech as a "school". Howard often makes references to his mother as being a "crazy old lady", but deep down, he is deeply attached to his mother and quite happy to be treated like a child. However, in one episode, Howard attempts to move out after a fight with his mother, but has serious delusions that she is trying to force him to stay, when in actuality, she is urging him to move out, which leads to him staying. It is also mentioned that she is on hormone replacement therapy and she wants to "play doctor" with Raj when he asks to sleep over.

When Howard reveals that he has proposed to Bernadette and she has accepted, she collapses, causing Howard to panic and dislocate his shoulder while trying to barge into the bathroom to help her. The timing leads him to believe that she may not like Bernadette (who is Catholic) and has suffered a heart attack from the shock of the news. In actuality, her fainting was due to food poisoning from the food she ate while meeting Bernadette and was completely unrelated to Howard's news. She has graciously accepted Bernadette as her daughter-in-law and is impressed by Bernadette's doctorate.

In season 7, Mrs. Wolowitz breaks her leg and keeps driving away the nurses hired to care for her. Even Penny rejects the job of caregiver after a very short time. After Stuart's comic book store burns down, Howard invites Stuart to work for Mrs. Wolowitz; however, they develop a strange relationship, much to Howard's annoyance.

Following the death of Carol Ann Susi, producers decided that Mrs. Wolowitz would die in the season 8 episode "The Comic Book Store Regeneration". Howard receives a phone call while in the comic book store from his aunt Gladys in Florida, whom Mrs. Wolowitz had gone to visit. She says that Mrs. Wolowitz lay down for a nap and never woke up afterwards. Howard and Bernadette then move back into Howard's old home, and Stuart decides to stay with them. He eventually moves out halfway through season 9.

Zack Johnson

Zack Johnson (Brian Thomas Smith), a dim-witted but friendly beefcake-type whom Penny dates on and off after her second break-up with Leonard. Zack works as the menu designer for restaurants that are owned by or which have hired his father's company to design their menus.

In season 3, Leonard invites Penny and Zack up to the roof to watch his experiment of bouncing laser beams off the moon; Zack misunderstands what is happening, and thinks they are going to blow up the moon.^[63] Later, he and Penny go out to a party, but she is so put off at how stupid he is that she runs back to Leonard for sex, saying he ruined her ability to tolerate stupid men.

In season 4, Zack runs into Penny, Bernadette, and Amy at a restaurant, and Amy becomes physically attracted to him. Sheldon arranges a meeting between Zack and Amy to satisfy her "urges", but his lack of intellect immediately discourages Amy. Unlike Penny's other boyfriends, Zack considers Leonard, Howard, Sheldon, and Raj (whom he calls "the science dudes") to be "cool" and makes a genuine effort to get to know them, even treating them as his friends. After accompanying them on a trip to the comic book store (where he and Raj bond over a mutual fondness for Archie comics), he enters a New Year's Eve costume party with them, portraying Superman in their version of the Justice League. In "The Toast Derivation", Sheldon invites him over for a party, where he bonds with Kripke and Stuart as well.

In season 7, it is revealed that he was unknowingly married to Penny for three years after the two were intoxicated and attended a wedding chapel in Las Vegas (they were not aware that weddings in Las Vegas are real). Penny invites him to Mrs. Wolowitz's house for Thanksgiving, where they get the marriage annulled.

In season 9, episode 22, Zack's observations indicate he is, in some respects, more observant and smarter than "the science dudes".

Minor characters

• Althea (Vernee Watson) A character who makes an appearance in the pilot episode as an attendant at a sperm bank, and then makes three appearances as an emergency room nurse in "The Peanut Reaction" episode (season 1) and "The Robotic Manipulation" episode (season 4), and as a ward nurse in "The Werewolf Transformation" (season 5). The name of the character is never used on the show, but is included on her name tag and in the credits. She is also the only character besides Leonard and Sheldon to be carried over from the original unaired pilot.

• Bert (Brian Posehn): A socially awkward geologist. His first appears in season 6, episode 18, "The Contractual Obligation Implementation", when he meets Raj and Lucy in the library during their date. Later in season 7, episode 13, "The Occupation Recalibration", he is found having a crush on Amy and tries to ask her out on a date to a geology rock show.

• Captain Sweatpants (Ian Scott Rudolph) and Lonely Larry (Owen Thayer): Two men sometimes seen at the guys' favorite comic book store.^[27][39] Captain Sweatpants is a middle-aged bald man who wears grey sweatpants and a City of Heroes T-shirt. Lonely Larry wears a brown suit and is extremely thin. They are also friends with Wil Wheaton. Both attend Howard's bachelor party.

• Cheryl (Erin Allin O'Reilly): Apparently a friend of one of Penny's friends (because it is subtly suggested she may not know many of the people at the party), who attends Penny's Halloween party in season 1, episode 6, "The Middle Earth Paradigm". Cheryl is the very talkative, short-haired brunette dressed as a ladybug, who shows interest in Raj. She is not identified within the episode, but her name is listed in the credits. She appears again as a Cheesecake Factory waitress in "The Pancake Batter Anomaly".

• Dale (Josh Brener): Dale works as a replacement for Stuart at the comic book store when he goes on a date with Amy "The Flaming Spittoon Acquisition", and also appears in "The Tangible Affection Proof" at Stuart's Valentine's Day party.

• Dan (Stephen Root): Bernadette (and later Penny)'s boss. Bernadette arranges an interview for Penny with Dan. The interview goes terribly, but Dan eventually hires Penny when they bond over their shared fear of Bernadette.

• Dimitri Rezinov (Pasha Lychnikoff): A Russian cosmonaut who is Howard's colleague on his Soyuz mission to the International Space Station.

• Wyatt (Keith Carradine): Penny's father. He comes to visit and Penny feels compelled to involve Leonard in a ruse to make him think that they are still together. (Wyatt reveals that he favors the successful Leonard over Penny's other "loser" boyfriends.) When the plot is revealed, he gets mad at Penny and feigns anger at Leonard. But after Penny leaves the room, he encourages Leonard to keep trying to get Penny back (because he wants his grandchildren to "grow up in a house without wheels"). Strangely though, in the first episode where Leonard's mother visits, Penny tearfully reveals her rough childhood, saying that Wyatt wanted a boy and even called her "slugger" until she reached puberty. Wyatt appears again in season 9, when Penny finally plucks up the courage to tell her father she eloped with Leonard. Wyatt is happy, but he also confesses that he killed Penny's pet pig a year ago.

Guest stars appearing as themselves

A number of Hollywood celebrities and famous scientists have made appearances as themselves.

• LeVar Burton: "The Toast Derivation", "The Habitation Configuration", "The Champagne Reflection"
• Nathan Fillion: "The Comic Book Store Regeneration"
• Carrie Fisher: "The Convention Conundrum"
• Ira Flatow: "The Vengeance Formulation", "The Discovery Dissipation"
• Summer Glau: "The Terminator Decoupling"
• Brian Greene: "The Herb Garden Germination"
• Stephen Hawking: "The Hawking Excitation", "The Extract Obliteration", "The Relationship Diremption", "The Troll Manifestation", "The Celebration Experimentation"
• James Earl Jones: "The Convention Conundrum"
• Stan Lee: "The Excelsior Acquisition"
• Mike Massimino: "The Friendship Contraction", "The Countdown Reflection", "The Decoupling Fluctuation", "The Re-Entry Minimization", "The First Pitch Insufficiency"
• Elon Musk: "The Platonic Permutation"
• Adam Nimoy: "The Spock Resonance"
• Bill Nye: "The Proton Displacement"
• Katee Sackhoff: "The Vengeance Formulation", "The Hot Troll Deviation"
• Charlie Sheen: "The Griffin Equivalency"
• Kevin Smith: "The Fortification Implementation"
• Brent Spiner: "The Russian Rocket Reaction"
• George Takei: "The Hot Troll Deviation"
• Neil deGrasse Tyson: "The Apology Insufficiency"
• Adam West:^[18] "The Celebration Experimentation"
• Steve Wozniak: "The Cruciferous Vegetable Amplification"

Notes

1. Although not seen or heard prior to season 4, President Siebert's name is mentioned in season 2.

References

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External links

• Official website