Type these in when the Muppets are racing over the logo and a trumpet will play if done correctly.

All Racers:
Press Circle, Triangle, X, Circle, Triangle, X, Circle, Triangle, Square, X.

All Racers and Vehicles:
Press Triangle, Circle, Triangle, Square, Triangle, X, Triangle, Triangle, X, Circle.

Unlock The Studio Track:
Press Square, Square, Circle, Circle, X, Circle, Triangle, Circle, Triangle, Square.

Unlock Arches Track:
Press Square, Circle, X, Circle, Square, Triangle, Circle, X, Circle, Triangle.

Unlock Fraggle Rock Track:
Press X, Square, X, Square, X, Square, Triangle, Circle, X, Square.

Unlock The End and Six Overhead Tracks:
Press Circle, Triangle, Square, Triangle, X, Triangle, Square, Circle, Triangle, X.

Final Stunt Level:
To unlock the last stunt level you need to get 100% on the game then go to SELECT COURSE then there you have it!

GameShark Codes

Mega Jump!
Just keep pressing jump to jump higher. Love, Lik 
800c35880040
   
Stop Race Timer
800b0a940000
   
Infinite Boost/Special Move
800c353201a4
   
Alway First Place
d10c35720000
800c35720001
   
Have All Cars
800e02bcffff
800e02beffff
   
Unlock Studio Track
800e02560161
   
Unlock Arches Track
800e025e0161
   
Unlock Fraggle Track
800e02660161
   
Unlock Disco Track
800e026e0161
   

        

Thanks to Revolution readers Andrew Greenup, Mzq and prules!