Infinite Continues
Press Up, Up, Down, Down, Left, Right, Left, Right, A + B at the Title Screen.

Defeat the Moth Boss
Pause game play and press B, A, B and A. The moth will fly away when the game is unpaused.

Infinite Power-Ups
Locate the falling drop claws, then crouch next to where they are landing. Face the claws and repeatedly punch in this direction. Each defeated claw will transform into a power-up. Use the pattern that the claws are falling to collect the heart, weapon bonus, or extra points before returning into position to hit defeat claws.