Press any of the following codes at the Title Screen, when you are done, you will hear a tone each time one is done correctly. If the Title Screen fades and the Demo starts, you will have to Reset the game and do them again.

Up, A, A, A, Down for every level to be completed.
B, A, B, Y for Super Jumps.
X, A, B, Y, Up, Down, to be Invincible.
B, Up, B, Select, Y, for 50 lives.
B, Left, Up, B, for 99 Diving Suits.
Right, Up, Select, Start, for 99 Portable Holes.
X, X, Up, Down, X, for 99 Smart Bombs.
B, A, LEFT, LEFT, for 99 Nerf Shots.