Peachy Peach is an item in Paper Mario: The Thousand-Year Door and Super Paper Mario. In Super Paper Mario, if Princess Peach eats a Pink Apple, she turns into a Peachy Peach.
In Paper Mario: The Thousand-Year Door you can only get a Peachy Peach by sleeping in the inn in Twilight Town. The Peachy Peach will only restore 1 HP and 2 FP when used. If you give Zess T. a Peachy Peach, she will make Fresh Juice.
In Super Paper Mario, The Peachy Peach's restorative power is greater than in the previous game; it heals 10 HP and cures Poison. Peachy Peaches can be bought at the Itty Bits store at The Dotwood Tree for 25 coins, or they can be purchased from Flimm for 19 coins if he has one.