Dance against Pander: 

In order to dance against Pander, who is the 
strangest dancer in the game, you have to get a 
fever time in every level up to Robo-Z Gold, and
then get one on her. It's hard to say what 
dancing against Pander gives you, but it must have
some soft of signifigance. It is visually one of 
the coolest levels in the game.