"When the arcade game Mortal Kombat was ported for home release on the Mega Drive and Super Nintendo Entertainment System, Nintendo decided to censor the game's gore, but Sega kept the content in the game, via a code entered at the start screen (A,B,A,C,A,B,B). Sega's gamble paid off, as its version of Mortal Kombat received generally higher and more favorable reviews in the gaming press and outsold the SNES version three to one." -
wikipedia