Cheat Menu- Get the cheat menu by holding L + C-Right + C-Down and pressing A.
Invisible Riders- Input the code INVISRIDER in the cheat menu.
Stunt Bonus- Input the code SHOWOFF in the cheat menu.
Big Head Mode- Input the code BLAHBLAH in the cheat menu.
All Stunts- Input the code TRICKSTER in the cheat menu.
Mirror Mode- Input the code YADAYADA in the cheat menu.
Night Mode- Input the code MIDNIGHT in the cheat menu.
Hill Climb Mode- Get 1st place in the gold round on the amateur session.
3D Mode- Get 1st place in the challenge round on pro season.
Soccer Mode- Get 1st place in the silver round on novice season.
1984 Excitebike- To have access to this you must complete the tutorial (NOTE- the track editor also works).