Level Select...
	Pause Cheat Codes...
	Secret Room...

At the title screen quickly press A, B, A, A, B, B, B, A, A, C, C, C.

Enter these codes while the game is paused.

Effect	Code
Both players invincible	C, A, Left, Right, A, B
Full energy for both players	Down, B, Up, B, B, A
Get upgraded weapons for both players	C, Right, A, B, B, Up
One life added for both players	Right, A, Down, C, A, Right
Play Level menu	Down, B, A, C, Down, Right

In the subway you can warp to a huge boss and tons of power ups. Walk through the third wall to get there.