Character select:
Hold L + R + Down at the status window. Press Start until the desired character is displayed. Hold L + R + Down. Hold X + Y while these buttons are held. Finally press B while all buttons remain held. Roid will be replaced by the new character. Note: The new character's mech will not be available for use.

Arena Town:
Highlight the "New Game" option at the main menu, then hold L + R then hold A + Up. Release all four buttons to get to the bonus Arena Town area.

Sound test:
Highlight the "Load Game" option at the main menu, then hold L + R then hold A + Down. Release all four buttons to display the sound test menu.