Whomp 'Em Cheats
Intentionally die immediately after starting game play. Continue the game to restart with another energy tank. Repeat this process again to start with three tanks.
Hold A + B on controller two and press Start on controller one at the title screen. Press Left or Right to select a sound and A to play it.
Secret Sound Test
At the title screen press and hold the A and B BUTTONS on controller 2 and press START on controller 1. The Character on the screen will smile and then bow his head, keep holding the A and B Buttons until the Sound Test appears. Now you can listen to any of the music tracks or sound effects used in the game.