At the main screen, press Up(2), Down(2), Left(2), Right(2).
Earn 15 stars in the game. Note: A star is awarded for every 200 points in a game.
Earn 25 stars in the game.
Select the Helmet game and begin on the easy difficulty setting. Intentionally lose before accumulating 100 points, then select the "Retry" option. The game will restart with Wario as a character.
Pause the game and press B.
Note: You must have a 2.1 or higher version of the Game Shark to use these codes in a Game Boy Color system.