Super Paper Mario/Chapter 2: Gloam Valley

Rescuing Peach
Go down the elevator
 * Flipside Tower

Follow Merlon.
 * Flipside 2nd Floor

It's Peach!
 * Flipside 3rd Floor

Go to the shop and buy 1 Fire Burst.
 * Flipside 2nd floor

Go to the kitchen and cook the Fire Burst.
 * Flipside 1st Floor

Feed the soup to Peach. Peach joins your party.
 * Flipside 3rd Floor