Full Health

Pause game and press: Up, Down, Right, Left, Sqaure (3x).

All Items

At the item select screen: Hold R1 & L1, and press Up, Square (2x), Left Square (2x), Down, Square (2x), Right, Square (2x).

All Multi-player Levels

At the V.S. or Co-op screen press: L1, R1, L2, R2, Square, L3, R3.

All Layouts

At the mission select screen press: R3, L3, R2, L2, R1, L1

All Characters

At the title screen press: L1, R2, L2, R1, Right, Left, L3, R3.

Bonus Stage

At the title screen press: L1, Up, R1, Down, L2, Right, R2, Left.