PO'ed Cheats

At the Delete Game menu, press A and Right, then press B and Up. Return to the main menu and witness the ending. This only works if you have at least one saved game.

Highlight a game from the load game menu. Press LS + RS + B to start the game. Levels with the Butthead monster will be modified by the code.

In the jetpack mode, bring up the weapon select menu and press L and Down/Right