Extra continues - Press Left,Left,B,B,B,C,C,C, Start at the title screen.

Final Boss Duel - When you get to the final boss playing 2-player mode, have one player choose ''yes'' and the other choose ''no''. You will be forced to duel against each other.

Get Bad Ending - Choose to be Mr X's right-hand man the first time you meet him. Then complete the game.

Level and Lives Select - Go to the main menu. Hold down (A) + (B) + (C) + RIGHT on controller 2 while selecting Options on controller 1 (best if done with two people). You can now select how many lives you start with and which stage to start on.