Ultra C

As of the 1968 olympics, Gymnastic feats were assigned a difficulty rating A-C, with A being easier than C. Since then, the difficulty ratings have expanded to be A-G. At the time, 'ultra-C' was the term the Japanese team used to describe their strategy, which ultimately brought them the gold medal that year, and the term stuck so well it entered the Japanese lexicon, below.

ウルトラＣ Noun 1. amazing feat; trump card; (something) earth-shattering. Colloquialism, Wasei, originated in Japan, during the 1968 Summer olympics. From English “ultra C”, C level having been the highest degree of difficulty in artistic gymnastics when the term was coined.

This phrase became the basis for many marketing campaigns, and even lent to the title of the show Ultra Q, and its sequel Ultraman.

http://ajw.asahi.com/article/views/vox/AJ201208030039