Select the "Extras" option at the main menu, then the "Cheats" option. Activate the following cheats by entering the corresponding codes:

CHEAT FUNCTION - CHEAT CODE
Invincibility in Story mode - Enter DOWN, DOWN, RIGHT, UP, LEFT as a code.
All multi-player characters - Enter LEFT, DOWN, LEFT, RIGHT, DOWN as a code.
All multi-player maps - Enter UP, UP, LEFT, DOWN, DOWN as a code.
Unlimited Chi - Enter DOWN, RIGHT, LEFT, UP, DOWN as a code.
4x damage multiplier - Enter UP, DOWN, UP, RIGHT, LEFT as a code.
Big heads in Story mode - Enter DOWN, UP, LEFT, RIGHT, RIGHT as a code.
Dragon Warrior costume in multi-player mode - Enter LEFT, DOWN, RIGHT, LEFT, UP as a code.
All costumes - Enter RIGHT, LEFT, DOWN, UP, RIGHT as a code.
Full upgrades - Enter LEFT, RIGHT, DOWN, LEFT, UP as a code.