Level Select:
At the title screen, press Square, Square, Square, Square, Square, Triangle, Triangle, Triangle, Triangle, Triangle, Triangle, Triangle, Circle, Circle, Circle.

Invincibility:
Pause the game & press Triangle, Triangle, X, X, Circle, Square, Circle, Square, Down, Left & resume the game. To turn it off, repeat the process.

Maximum Power:
Pause the game & press Up, Up, Down, Down, Left, Right, Left, Right, X, Circle & resume the game.