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
Use Dance Dance Revolution mat in Family mode
Insert two standard controllers and go into Family mode. Select "Dancing" then choose your song. Disconnect the controllers and choose your difficulties.