Soft Reset:
At any point press Start+Select+R1+R2+L1+L2.

Fat Spice:
At the Globe screen, hold down Start and press Circle, Square, Circle, Square.

Hand Bag Mode:
At the Globe screen, hold down Start and press Square, Triangle, Circle, Triangle Now there's some new moves at the dance studio.

Semi-Nude Title Screen:
At the Globe screen, hold down Start and press Circle, Triangle, Triangle, Circle. Then Soft Reset...

Thanks to Revolution readers Moodman!