Ryu Hayabusa's iconic Izuna Drop was inspired by a move from Sanpei Shirato's manga series Nukenin Kamui (Kamui Gaiden). The game's director, Tomonobu Itagaki, had to get formal permission from Shirato to include the move in the game. It has since been one of Hayabusa's staple attacks throughout all of the character's appearances.
Contributed by DrakeVagabond