At the main menu got to enter password and enter this to get Unlimited weapons, stage select, and play as monster. Do this code and you will get to cut the monsters in half only if you have a sword, anter at the options screen L1, R1, L2, R2, select.
Cheat mode
On the password screen, press: left, up, triangle, down, o, triangle, square, down. Once enabled you can select any level you wish, infinite continues or even choose to play as one monsters.
Small Creatures
Enable cheat mode. Press L2, L2, R1, R1, L1, R2, Select. A sound will confirm correct code entry. Switch the 'reduse' option on, then start the game with shrunken creatures.