Enter this code at the password screen when you start the
game and you will have the following options:

Unlimited Hearts
Power Ups/Weapons
Level Select
Play as a Monster!
LEFT,UP,TRIANGLE,DOWN,CIRCLE,TRIANGLE,
SQUARE,DOWN

Baby Monsters
First you must enter the level select code (L1,L1,L2,R1,R1,R2,Select) After that tap L2,L2,R1,R1,L1,R2,Select now begin a game you there should be a baby monster code