Level select:
Press Down + Start on controller one and Right on controller two simultaneously.

Borrowed life:
Start a two player game. Press A + B after running out of lives to borrow one life from the other player.

Double weapon:
Start a two player game. Have both players collect a weapon simultaneously. The weapon will be usable by both players.

Hint: Defeating Bosses:
Shoot the Bosses when they are attacking your character. The Boss will flash if its weak spot is hit. The laser may be the best weapon to use against the Bosses.

Hugger: Shoot him in the chest his coat opens to shoot.

Asophy: Shoot him while he is large in his open mouth.

Tacady: Shoot its eye socket after the eyes are out.

Teetsie: Shoot the middle of its body.

Minemor: Shoot the red part of its body.

King Core: Shoot the blue head that spins around its body.