Donkey Kong 64 Cheats

Go to the minigame selection screen in Snide's HQ (needs to be unlocked first) and hit A and B at the same time. If done right, you should be brought to a secret area that the developers probably used to test out the game mechanics. If you try to run out of this area, you will just be warped back to the starting point. So to leave this area, you must reset the game.