List of fictional extraterrestrials by form

This is a List of fictional alien lifeforms from science fiction by physical features or form.

Ancient races

Aquatic creatures

Amorphous creatures

The amorphous creature is a common trope in science fiction. Usually it is depicted as a living mass of jelly, slime or liquid-like substance that can take any shape it wants.
Amorphous creatures are to be distinguished from shape-shifters that can change their appearance due to their body material to mimic a living or non-living thing however they like.
Metaphorically, "amorphous" refers to any structure, body, figure, text or speech that lacks a distinct form or order. In Japan most amorphous creatures (especially those made of liquids) are called Slimes.

• Aliens from the Sector General novel series by James White are among the most diverse. Crystalline methane creatures, continent sized carpets, rolling ring-shaped aliens, chlorine breathers, radiation eating telepaths and creatures assembled from several symbiont species meet in a setting of space hospital.
• "Blob" (The Blob) Perhaps the most familiar example of an amorphous extraterrestrial creature
• The blobels from Philip K. Dick's short story Oh, to Be a Blobel!
• Dralasite - An amoeboid race introduced in Star Frontiers
• Dubtak, creatures resembling manta rays but with lots of little legs (Ascendancy)
• Ghatanothoa of H. P. Lovecraft (has Gorgon-like visual properties)
• Galvanic Mechamorph (Ben 10)
• Polymorph (Ben 10: Alien Force)
• Nestene Consciousness (Doctor Who), a race of large amorphous creatures made of living plastic, and are thus capable of controlling all things made from plastic
• Shoggoths from the H. P. Lovecraft's Cthulhu Mythos
• Trisolian, humanoid creatures made out of liquid (Futurama)
• Umgah, large, pink or lilac-colored blobs (Star Control)
• Vermicious knids from Charlie and the Great Glass Elevator
• A giant pasty mass of protoplasm found in Venusian jungles in one of Stanley G. Weinbaum's few short stories
• The body-dissolving alien in Damon Knight's Four into one short story
• The Rutans from Doctor Who
• The Vom, a large black blob not unlike a gigantic amoeba, impervious to almost all energy and physical attack

Energy beings

• Anodite (Ben 10)
• Celareon, energy beings encased in metal bodies. (Conquest: Frontier Wars)
• Drej (Titan A.E.)
• Eldila, barely visible faint, shifting light that are native to interplanetary space. (Space Trilogy)
• Father - an intelligent sponge-like entity formed from a network of algae and alien corpses spread across an ocean planet. (Animorphs)
• Prypiatosian-B (Ben 10: Ultimate Alien)
• Zoni (Ratchet & Clank)
• Wisp, colorful little aliens that give you amazing abilities, they are from Sonic Colors

Extra-dimensional beings

• Ancient (after Ascension) - Stargate
• Combine "Advisor" aka Shu'ulathoi from Half Life 2 (Half-Life)
• Imp (DC Comics)
• Annihilus (Marvel Comics)
• The Anti-Monitor (DC Comics)
• Arilou (Star Control)
• Bakugan (Bakugan)
• Blastaar (Marvel Comics)
• Celestial Toymaker (Doctor Who)
• Chaos God (Warhammer 40,000)
• Daemon (Warhammer 40,000)
• Hounds of Tindalos - Mysterious, angular, timeless beings with no accurate given description. (Frank Belknap Long)
• Krang (Teenage Mutant Ninja Turtles)
• Krith (Timeliner)
• Lawbringers (Crossgen)
• Magolor (Kirby's Return to Dream Land)
• nDs (Invasion: Earth)
• Orbulon (WarioWare)
• Orz (Star Control)
• Q (Star Trek)
• Qwardian (DC Comics)
• Reaper (Doctor Who)
• Sau-Bau (Battlelords of the 23rd Century)
• Servitors of the Outer Gods (H. P. Lovecraft)
• Species 8472 (Star Trek)
• Sphere Builder (Star Trek)
• The Spineless Ones (Marvel Comics) - see also Mojo
• Technet (Marvel Comics)
• The Voice in the Darkness (Starcraft)
• "Them" (The Homeward Bounders by Diana Wynne Jones)
• Unnamed telepathic aliens of Babylon 5: Thirdspace
• Warwolves (Marvel Comics)
• Warp entities (Warhammer 40,000)
• Zoni (Ratchet & Clank)
• Bill Cipher (Gravity Falls)

Gaseous creatures

• Black Cloud (Fred Hoyle) (interstellar dust cloud)
• Dark Matter - One eyed possessing black clouds in space in the Kirby series
• Gelth, intelligent gaseous lifeforms; were once solid, but were altered as a result of the Time War (Doctor Who)
• The Invaders, higher-dimensional beings originating from a gas giant. (Eight Worlds)
• Nimbuloids, a species of large sentient gas creatures (Ascendancy)
• Beta Renner cloud (Star Trek)
• Dikironium cloud - Intelligent "vampire cloud" (Star Trek)

Immaterial/Incorporeal beings

• The Animus, a telepathic alien intelligence with a corporeal form resembling an octopus (Doctor Who)
• Beta-7, a hive mind appearing always in the same, humanoid, form, (Rick and Morty)
• Caleban - invisible telepathic beings who are actually the minds of stars (Whipping Star)
• Celestialsapien (Ben 10: Alien Force)
• Cosmic entities (DC Comics)
• Cosmic entities (Marvel Comics)
• C'tan - 'Star Vampires' worshiped and given corporeal form by the Necrontyr, only four still exist, only two of which (the Nightbringer and the Deceiver) are active, Mars (The Void Dragon) is believed to be one that was covered by space dust over trillions of years ago. (Warhammer 40,000)
• Dnyarri, non-humanoid Telepaths (Star Control)
• Ectonurite (Ben 10)
• Grog - conical sessile sentient telepaths (Known Space)
• Govorom - Feminine-like spirits of nature (Ascendancy)
• Hooloovoo, non-corporeal beings who, when refracted in a prism, appear as a shade of blue. (The Hitchhiker's Guide to the Galaxy)
• Humanoid Interface (Haruhi Suzumiya)
• The Loki - A race of malevolent spirits that require hosts to survive. (Ratchet & Clank)
• Ly-Cilph - begin their lives as corporeal, but can latter become non-corporeal being. (Night's Dawn Trilogy)
• "Phantoms" - A ghost-like race. (Final Fantasy: The Spirits Within)
• Magius (Valvrave the Liberator)
• Medusan, an incorporeal race that cannot be looked at by humanoids, or their appearance will drive you insane (Star Trek)
• Prophet (Star Trek)
• Q - all individuals of the Q Continuum which is accessible to the "Q" and their guests, and the true nature of it is said to be beyond the comprehension of "lesser beings" such as humans so it is shown to humans only in ways they can understand. (Star Trek)
• Unity, a hive mind bent on bringing universal peace by taking over the mind of every living being, it seems to have a more feminine personality, and is involved romantically with Rick Sanchez, a single minded human from earth (Rick and Morty)
• Watchers In The Dark (highly telepathic creatures that inhabit the ruins of Caliban, home of the Dark Angels Space Marine Chapter) (Warhammer 40,000)

Invertebrates

Arthropods

Cephalopods

• Ceph - It's theorized that they are not actual beings, but tools of a more advanced race. (Crysis)
• Edestekai, a tri-lateral primitive race encountered. (Star Frontiers)
• Mars People, intelligent creatures resembling squids or octopi, sporting a great amount of tendril-like tentacles. (Metal Slug)
• Martian (The War of the Worlds)
• Ul-Mor, a race of sentient land-dwelling octopus-like nomads encountered. (Star Frontiers)
• Vicetopus (Ben 10: Omniverse)
• Zoq-Fot-Pik (Star Control)

Medusozoans

• Abyormenite - floating balloons (Cycle of Fire)
• Amperi (Ben 10: Ultimate Alien)
• Chronomyst - sentient jellyfish-like creatures that communicate by refracting light within their bodies. (Ascendancy)

Worms

• Chtorr - Pink wormlike creatures. According to David, the Chtorr can also refer to the entire alien ecology. (War Against the Chtorr)
• Harmonia (The Sirens of Titan), a cave-dwelling flatworm-like race living on Mercury.
• Lekgolo (Halo)
  • Mgalekgolo - Beings composed of multiple Lekgolo worms that, together, form a single, sentient organism. (Halo)
• Sandworm (Dune)
• Yuggs (H. P. Lovecraft)

Others

• Garrotian Snail (Noon Universe)
• Great Race of Yith of H. P. Lovecraft (Disembodied, time-hopping minds of a long-dead alien race; Known bodies used are gigantic molluscs and large beetles)
• Hiver (Traveller) (modified starfish)
• Rigellians (Lensman books) which are barrel-shaped with four tentacular arms and four stubby legs
• Kambuchka (Ascendancy)
• Mebes - Giant single-celled sentient organisms. (Ascendancy)
• Orishan (Ben 10: Ultimate Alien)
• Spathi, similar to shellfish (Star Control)
• Destroyah, a mutant crustacean (Godzilla vs. Destoroyah)
• Thep Khufan - Mummy-like aliens composed completely out of bandages. (Ben 10)
• Tralfamadorian (The Sirens of Titan, Slaughterhouse 5)
• Utrom (Teenage Mutant Ninja Turtles)
• VUX, green tentacular creatures (Star Control)

Living planets

Microscopic life

• The Flood - The LF.Xx.3273 Flood Super Cell is capable of infecting victims on its own. (Halo)
• Martian - sentient cloudlets composed of countless microscopic particles (Last and First Men)
• "Thing" (The Thing)
• Hoth virus (Stargate)

Non-sentient creatures

Other inorganic life

• Aliens that are product of mechanical evolution (The Invincible)
• Blue Meanies, armoured creatures that live on Mother, created to care for her (Remnants)
• Chenjesu - intelligent silicon-based crystals (Star Control)
• Crystalsapien (Ben 10: Alien Force)
• Gadmeer - Beings that live in a sulphur environment. (Stargate)
• Gems - a race of sapient gemstones who generate functional humanoid bodies around themselves using solid light. (Steven Universe)
• Horta - silicon-based tunneler. (Star Trek)
• Ogri - silicon-based life form resembling standing stones (Doctor Who)
• The Scrin - an intelligent species of unknown form which are apparently symbiotic with the crystal, root and spore, Tiberium. (Command & Conquer)
• Segmentasapien (Ben 10: Omniverse)
• Sonorosian (Ben 10: Alien Force)
• Shevar - an inorganic race from an alternate universe that feeds on life force. (Ascendancy)
• Silicoid - a race of sentient crystals. (Master of Orion)
• Sphere (Sphere)
• Galilean (Ben 10: Omniverse)
• Petrosapien (Ben 10)
• Tholian (Star Trek)
• Trillions of Nicholas Fisk - small collective crystals

Space-living creatures

These fictional creatures purport to thrive in the biome of outer space.

• Acanti (Marvel Comics)
• Bentusi (Homeworld)
• Budong (Farscape)
• Cromulons (Rick and Morty)
• Forerunners (The History of the Galaxy)
• Farpoint Station (Star Trek)
• Gomtuu (Star Trek)
• Leviathan (Farscape)
• The Lexx race (Lexx)
• Necrofriggian (Ben 10)
• Rigelatin (Duke Nukem II)
• Star Whale (Doctor Who)
• Oswaft (Star Wars)
• Outsider (Known Space)
• Sahaquiel (Neon Genesis Evangelion)
• To'kustar (Ben 10)

Shapeshifters

Shape-shifters can change their appearance due to their body material to mimic a living or non-living thing.

• Aylee (Sluggy Freelance) - Shapeshifts every stage of the life cycle.
• Capelons (Ascendancy)
• Clawdite (Star Wars)
• Chameloid (Star Trek)
• Changeling (Star Trek)
• Changers (Consider Phlebas)
• Darlok (Master of Orion)
• Durlans, the race of Chameleon Boy from the Legion of Super-Heroes (DC Comics)
• ELS, Extraterrestrial Living-metal Shape-shifter (Mobile Suit Gundam 00 the Movie: Awakening of the Trailblazer) - A race of techno-organic sentient aliens.
• The Flood (Halo)
• Green Martian (DC Comics)
• High Ones (Elfquest)
• Krillitane (Doctor Who)
• Limax (Ben 10)
• Makluan (Marvel Comics) - see also Fin Fang Foom
• Mangalore (The Fifth Element)
• Martians (Invincible) - see Shapesmith
• Mazian (Battlelords of the 23rd Century)
• Plasmavore (Doctor Who)
• Human Is is a science fiction short story by Philip K. Dick in which a woman whose cold and emotionally abusive husband returns from a survey mission to the dying planet Rexor IV, and is changed for the better - it is later revealed that his psyche was replaced by a Rexorian, glad to have escaped the confines of its dying planet.
• In Invasion of the Pod People Pod People grow in large seed pods and gradually take the form of a particular person, eventually taking over their bodies once the growth process is complete
• Rutan (Doctor Who)
• Serleena is the main antagonist of Men in Black II - an attrictve looking, evil, shapeshifting "Kylothian" queen
• Silkie (The Silkie)
• Skrull (Marvel Comics)
• Star Kings (Star King)
• Time Lord/Gallifreyan (Doctor Who) - see Regeneration
• "Thing" (The Thing)
• Uryuom (El Goonish Shive)
• Vladat (Ben 10: Omniverse)
• White Martian (DC Comics)
• Zygon (Doctor Who)
• The 1953 short story Colony by Philip K. Dick features a predatory alien life form that is capable of precise mimicry of all kinds of objects. The size and complexity of the mimicked object can varies with the larger ones usually trying to trap and consume humans similar to carnivorous plants.
• In the 1954 short story The Father-thing by Philip K. Dick aliens replace and mimic humans. Dick's story is typically more personal because it is not about the (alien) invasion of a community, but of a family.
• In Invasion of the Body Snatchers a town in California is being invaded by seeds that have drifted to Earth from space. The seeds replace sleeping people with perfect physical duplicates grown from plantlike pods, while their human victims turn to dust. The novel by Jack Finney also has multiple film adaptions: Invasion of the Body Snatchers (1956), Invasion of the Body Snatchers (1978), Body Snatchers (1993), The Invasion (2007)
• In Who Goes There? a novel by John W. Campbell, Jr a revived alien that was found crashed in Antarctica can assume the shape, memories, and personality of any living thing it devours.
• Guardians for the Royal Four Roswell(TV Show)

Parasites

Plants and fungi

Robotic life

Vertebrates

Avians

• Amarantin (Revelation Space)
• Chozo (Metroid)
• Turians (Mass Effect)
• Kickin Hawk's Species (Ben 10: Omniverse)
• Kig-Yar (Halo)
• Omnivoracious (Ben 10: Omniverse)
• Pkunk, appear like Toucans (Star Control)
• Ythrians from Poul Anderson's Technic History. Similar to eagles in some ways.

• Xindi-Avians (Star Trek: Enterprise)

Humanoids

Mammalians

Reptilians and amphibians

Others

• The Doublers, two-in-one semi-humanoids of Stanisław Lem's Eden
• Dug (Star Wars)
• The Face of Boe, a giant head in a jar-like support system (Doctor Who)
• Lloigor (Return of the Lloigor) (Vortices of energy; Solidify as vast, alien reptiles)
• Logrian (The History of the Galaxy) (two-headed xenomorphs)
• Osakar - four-legged non-centauroid race of genetically identical individuals. (Star Frontiers)
• Orfa (Ascendancy)
• Photino Birds, made up of Dark Matter (Xeelee Squence)
• Puppeteer, creatures with three legs and two manipulative heads. (Ringworld)(Known Space)
• Pilots (Farscape)
• Slitheen (or, more accurately, Raxicoricofallopatorians — Slitheen is a family name, not the species), bipedal, vaguely humanoid creatures with sharp claws and baby-like faces, made of living calcium (Doctor Who)
• Snovemdoma, similar to mammoths. (Ascendancy)
• Swaparaman (Ascendancy)
• Spline, whalelike creatures that rebuilt themselves into living ships (Xeelee Sequence)

Others

• Atrocian (Ben 10: Omniverse]])
• Ark Megaforms (Noon Universe)
• Arburian Pelarota (Ben 10)
• Dyson Aliens (Peter F. Hamilton's "Pandora's Star")
• Meehook (Fusion)
• Giygas (EarthBound) (Mother 2)
• Gimlinopithecus (Ben 10: Ultimate Alien)
• Galvanic Mechamorph (Ben 10)
• Melnorme (Star Control)
• Nemuina (Ben 10: Omniverse)
• Oankali (Xenogenesis)
• Pan Spechi, each individual has five different bodies, occupying each one throughout their lifetime. (ConSentiency universe)
• Precursor (Halo)
• Mr. Saturn (EarthBound)
• Taprisiots (Whipping Star, The Dosadi Experiment)
• Tweel from A Martian Odyssey
• Zebesian Space Pirates (Metroid series — the species has a wide range of morphological variety)

References