Choose the "Options" selection at the main menu, then press L or R to cycle from the "Game Settings" option until the "Cheats" option appears. Then, press Down until the desired cheat option appears. Press B to display a keyboard that is used to enter the code to unlock that cheat option.
Enter "CLAPPEDOUT" as a code for the "Character Completion" option at the "Cheats" screen. All bonuses in the game will now be unlocked.50cc and 500cc Classes
Enter "SQUIRRELDOG" as a code for the "50 cc Class" option at the "Cheats" screen.Pro Physics
Enter "SWAPPIN" as a code for the "Pro Physics" option at the "Cheats" screen.