First have at least two controllers plugged in to enable 
the 'MULTI' option. Then enter the Big Cheat in the cheat 
menu (BEWAREOBLIVIONISATHAND)

Now, go into Multi, and start a game on any level. When 
the game begins, go into the Cheats menu, and scroll 
through the "warp to ..." and select the level you 
want to play.

NOTES: This is kind of buggy, but works on most levels 
and bosses. Avoid teleporters as they tend to mess it up. 
Submitted by Noah Hennig and Matt Grossman

Fruit Stripes 
To make your character wear fruity strips put this code 
in the enter cheat menu: FROOTSTRIPE