At the Bonus Items Menu, enter the following "Codes" for Free Race mode:

Cheat - Effect

MUSCLE-Extra Power
MOON-Low Gravity
BACKWARDS-Mirrored Tracks
STRETCH-Double Height Suspension
ONE2MANY-Blurry Motion
SHINY-Chrome Cars
NITRO-Nitrous Oxide Booster
DRIVER-70s-Style Springy Suspension
KABOOM-Exploding Kerbs
BRICK-Invincible Car
DOTTY-Tough Bonus Cars