The Game Boy version included in the box a metallic pendant with the Killer Instinct logo engraved on it.
One of the unique features of the SNES version of Killer Instinct is that the game itself is a black colored cartridge. Most SNES games were a plain, gray color.
Killer Instinct was originally developed for arcades as a prototype to the Ultra 64, later renamed the Nintendo 64. When the 64 project was delayed, Nintendo went ahead and released the SNES port instead.
Killer Instinct also comes packed with a soundtrack CD, titled Killer Cuts, which features remixed music based on the background and main themes found in the game.
For the transition to the SNES, the only major item missing is the 3D animated cut-scenes. They are replaced here by stills of the animations for the VS. and winner screens.
Missing from the Gameboy version are, of course, every animated cutscene, plus two characters: Cinder and Riptor.