National Videogame Museum - You put cartridges in your console, you put cartridges in your Game Boy, but how about putting cartridges in your controller? This is the Mortal Kombat II Kontrol
Mortal Kombat II The Arcade Version - Mortal Kombat Secrets
Controls - Mortal Kombat 2 Guide - IGN
02160: mk2r14: Pressing P2 button six causes the game to hang - MAME Testers