During game play press "Select", then highlight Help and press, L2, L1, L2, Square, Circle, Square. Now you can put the following codes:
Unlimited Health: R3,L3,R3,Circle
One Hit Kills: L3,R3,Circle,Square
Mini Mode: L3,R3,Square,Circle
Big Head: Start,Square,Circle,Start
Godzilla Mode: R3,Square,Circle,L3
Finish Level L2, L1, L2, Square, Circle, Square, L3, R3, L2, L1
Power Mode L2, L1, L2, Square, Circle, Square, R3, L3, Circle, Square
Phase Cloaks Unlimited L2, L1, Square, Circle, Square, L1, R3, L2, L3
Large Characters L2, L1, L2, Square, Circle, Square, R3, Square, Circle, L3
Pick Character L2, L1, L2, Square, Circle, Square, L2, L2, L2, L2