Infinite powers
To get infinite Heat vision, X-ray Vision, Freeze Breath & Speed, press and hold A, B, C-Down, C-Up, at the title screen then press Start.
Level Select
Play until you can save your game then save, reset and load your game. When it asks to enter Rumble Pak press B then A.
Cheat Mode
To activate Cheat Mode, push: up-C, left-C, down-C, right-C at the main menu. To enable the cheats, press Start and the following buttons:
Level Skip - C-Up, C-Down
Refill health - Z-trigger, R
Super-Breath - Z-trigger, L
Super-Speed and Flight - R, Z-trigger
Super-Strength - L, Z-trigger
X-Ray Vision - R, L
Car Mode
At start of game go to the options menu. Then select practice. When you get there first get the guy with the gun out of your way because he might mess you up. After he's dead pick up the car and fly through all the rings even through the last one, you can't simply walk through it. If you successfully did this there will be a glitch in the game and you will be in the car.