Enter the following during gameplay:

Code - Effect

Up, Left, Down, Left, Down, Up, Up, Left - Big heads
L1, Left, L1, Left, R1, Right, R1, Right - Disco Mode
Up, Up, Up, Up, Up, Up, Down, Right, Up - Low Gravity

All team members must beat an episode with 100%: Defeat Leader In Single Player Mode upgrade a weapon with a character and do not miss during the level: Humans and Creatures.