After you beat the game wait for the title screen to come up again, don't turn off the game. Then enter the password 1MORELVL to play a short and intresting bonus level.
To enter the cheat code screen enter the password "Heybuddy" and the cheat code screen will appear. This screen lets you choose what level you wish to start at, where in the level, infinite health, and all weapons.
To access the Debug Mode, first enter the password HEYBUDDY in at the password screen. A new menu will pop up allowing you to select any stage, any area, turn invincibility on or off, and enable all weapons.
To start on any level, enter the password "Hevyfeet".
Kody's PlayStation Codes