Garfield: Caught In The Act Codes -

Level	Name	Password
2	The Curse of Cleofatra	Garfield, Odie, Irma
3	Count Slobula's Castle	Chicken, Jon, Pooky
4	The Revenge of Orange Beard 1	Monster, Arlene, Mouse
5	The Revenge of Orange Beard 2	Odie, Pooky, Arlene
6	Catsablanca	Jon, Irma, Garfield
7	Alien Landscape	Mouse, Chicken, Monster

Glitch: Invincibility:
After entering the multi-command, pause the game, then press [Jump]. Now you can do anything but die or kill. To get out of this state, press [Shoot].