When the player presses Start at the title screen of the NES verison, the game checks for the string "© konami" in VRAM. If the check fails, a flag is set, making the game's final boss, Shredder, much more difficult to beat. If the player manages to defeat this harder version of Shredder, the game will restart at the beginning of the fight.
At one point, Aska was originally intended to be "Mitsu", sharing a similar name of said character from Teenage Mutant Ninja Turtles III. However due to poor reception of the third film, the idea was dropped.
Aska, from the SNES version, is wearing a thong as part of her leotard in the Japanese release. These were changed to shorts in all other releases. For her victory pose, in the Japanese version she spins, then thrusts out her chest, causing her breasts to bounce. Internationally, she simply folds her arms.