press the following buttons on the min menu to play as a baby.
right,square,up,up,r2.

Small players = Square, R2, Right, L2, L1
Big heads = Triangle, Triangle, L2, L1, L1
Alternate clothes = Circle, L2, Left, R2, Triangle
Black/white mode = Up, R1, L2, R1, R2
Head as ball = Left, L1, L1, L1, R2
Topless = Down, R2, R2, R2, Triangle
Small heads = R2, Down, L2, L1, Circle
70's mode = L1, R2, L2, Circle, R1