Collect a certain number of gold medals to unlock a in-game movie you can watch:
Effect - Code
All Together Now - 33 Gold Medals
Amigo Racing - 15 Gold Medals
Boogie Wonderland - 21 Gold Medals
Driving Gloria Away - 26 Gold Medals
Mumble the Outsider - 06 Gold Medals
Out of the Egg - 01 Gold Medal
Somebody to Love - 12 Gold Medals
The Zoo - 31 Gold Medals
Insert two standard controllers and go into Family mode. Select "Dancing" then choose your song. Disconnect the controllers and choose your difficulties.