I have been working my way through this game, too. Although I've completed the main Adventure, I would like to use some cheats to unlock the special characters. Based on searches in this forum, it looks like none of the codes work, and from looking at published GameShark codes for the game, it looks like some of the addresses are off.
I'm planning on looking a bit tonight to see if I can fix the codes, and if I have any luck, I'll post my new ones.
In the meantime, try using TipTup the turle or Pipsy the mouse to race, and if you're really stuck, use the a-button trick to beat him.