At the Main Menu, type any of the following codes:

Cheat Code - Granted Wish

GOKARTZ - Small Wheels on Vehicles
BIGFOOTZ - Large Wheels on Vehicles
BIGHEADZ - Drivers Have Large Heads
BOXERZ - Drivers Have Large Hands and Feet
FONEKART - Secret Level
SPEEDRACER - Fast Race
TERRAFORMERS - Track Generator
INEEDMOREMAPS - All Tracks
INEEDMORECARS - Unlock Everything Except Generators