Type "THE PERFECT KISS" on the title screen. Now you can start the game with infinite weapons while you're the wolfman. If you type "SOULPSYCHEDELICIDE", you'll gain infinite extends.

NOTE: You may only have one of the above activated at a time. The original author suggested you use one of the 1st two and when you're on you last life and close to death type the 3rd one. Now go to the option screen and type the second one. This will allow you to continue at the last level completed and give you a full active life meter. Repeat if needed.