Cheat Code Screen
     At the Main Menu, hold L + C-Right + C-Down and press A.

Various Cheats
     At the Cheat Menu, enter any of the following "Codes":

Code                     Effect 
INVISRIDER               All Riders Invisible 
BLAHBLAH                 Big Head Mode 
SHOWOFF                  Stunt Bonus 
TRICKSTER                All Stunts 
YADAYADA                 Mirror Mode 
MIDNIGHT                 Night Mode 
PINHEAD                  Small Head Mode 
PATWELLS                 Beat This! Mode 
UGLYMUGS                 Developer Team Photo 
MOWER                    Invincibility 
XLURIDER                 Transparent Rider 
IMGOINGNOW               Debug Mode 
ROTCOLS                  Strange Colors 
WHEEEEEEEE               Downhill Mode