Invincibility:
At the title screen, press, Up, Down, Down, B, A, A, Down, Up, Left, B.

Unlock Race Mode:
Perform at least four good deeds. Once race mode is unlocked you can race for tokens with which you can buy the following bonuses: Chalk Mode, Crude Oil Mode, Cyber Shadows, Fast Mode, Infinite Flame, Infinite Gas, Invulnerability, Leak Mode, Low Gravity, Money For Merlin, Plastic Mode, Super Flatulence, and Super Strength.

Thanks to Revolution readers Rick Cagnolatti and David Dinsdale!