> In the Cat Walk event, highlight which song you wish to play and press Option.  Now, you'll play in Felicia's alternate color and the arrow icons and notes will be replaced with mice, bells, and fish.
(courtesy: GameFan)

> Before the Target 9 event begins, press and hold the Option button.  You'll now play as Fio in the event (though it doesn't make a huge difference).
(courtesy: GameFan)