Karai was notorious as an extremely difficult boss to defeat (especially on Genesis) and is a secret player character in the SNES version (in the Genesis version she is only unlockable with the use of a cheat device) where she can be unlocked by the use of a cheat code. Because of the relative obscurity of the TMNT Mirage comics (as compared to the 1987 cartoon, the Archie Comics and the films), many players at the time didn't recognize Karai in Tournament Fighters, and assumed her to be an original character created by Konami for the game.
- In the story mode of the SNES version, "Master Karai" (who is not known to the Turtles) arrives in New York with "the forces of the Shredder Elite" in order to avenge the Shredder, and kidnaps Splinter and April O'Neil to lure the Turtles into fighting her minions (oddly with the Shredder himself as the game's sub-boss); before her boss fight, Splinter says Karai "posseses super human powers." In the Tournament mode, "a very strong fighter by the name of 'Karai'" is announced by April to be "still alive" and challenges the winner of the titular fighting tournament to fight her, making her the final boss to beat. Her appearance in the SNES version is roughly based on the one from the Mirage comics but her in-game design is androgynous and confusingly masculine, leading some players at that time (and even Nintendo Power's strategy review) to assume it was a male character.
- In the Genesis version Karai, looks much more feminine than in the SNES game (quite similar to the SNES version's original character Aska) appearing with brown hair and wearing samurai-style armor without a helmet or blades with bare thighs and a thong. She also has a different backstory in the Genesis game, in which she sent the Turtles' clones to kidnap Splinter into Dimension X. She suddenly reveals herself to be the true mastermind behind this at the end of the game, following the player's defeat of Krang. In addition, the regular ending has Karai saying that it was only her clone that had been destroyed. As she can be truly killed only in the alternative ending after finishing the game at the hardest difficulty setting.
- The kanji on the lower level of her stage in the Genesis version, reads "忍", meaning endure or persevere, and is the first character in "Ninja".