The first time I played Mortal Kombat [official site], Nintendo had replaced all the blood with sweat, which seems like the kind of extreme detox plan Gwyneth Paltrow might be promoting next week. Instead of actually playing the game, I spent all of my time trying to figure out how to enter the cheat code that would activate the gore and fatalities, little realising that such a code only existed on the Genesis version of the game. The SNES was Sweat City forever.
These days, the cool kids edit files instead of entering cheat codes. A redditor by the name of XVermillion has unlocked previously unplayable characters Rain, Sindel and Baraka by renaming references to assets in the source files. Instructions are here.