Select two player mode, then have player one press L1 + R1 + X + Left Analog-stick Forward and player two repeatedly press Select simultaneously during game play.
Fat players
Select two player mode, then have player one press L1 + R1 + Square + Left Analog-stick Forward and player two repeatedly press Select simultaneously during game play.
Gorilla players
Select two player mode, then have player one press L1 + R1 + Circle + Left Analog-stick Forward and player two repeatedly press Select simultaneously during game play.
Thin players
Select two player mode, then have player one press L1 + R1 + Left Analog-stick Forward and player two repeatedly press Select simultaneously during game play.
Unlock Origan
At the start menu press SQUARE, SQUARE, SQUARE, TRIANGLE, TRIANGLE, TRIANGLE, and then press CIRCLE, CIRCLE, CIRCLE, UP, UP, UP, DOWN, LEFT, LEFT.
Big and small players...