Move in front of the bookcase inside Casper's house. Shoot the bookcase with normal, fire, fire, ice, normal, fire, and super spirit blasts (in order). The will open to a secret room containing Lucky the Chicken.
Game Shark Codes
Master Code (Must Be On) ECB52F58 14345B9C
Infinite Shield Energy 4CC88EE8 1456E7A8
Infinite Comet Energy 4CC88EE0 1456E751