Peewee Piranha is the first boss encountered in Super Mario Galaxy 2. He appears in the first galaxy, the Sky Station Galaxy, where he rests in a massive egg on the final planet. Once Mario lands on the planet, the egg will crack, leaving only a fragment of it still sticking on Peewee Piranha's rear, similar to a diaper.
Even though a baby, Peewee Piranha's size is still very large. He resembles a giant Piranha Plant with two green legs, which are still inside the leg except for the feet. Peewee Piranha, unlike normal Piranha Plants, has pink skin with white dots. Circling around the top of his head are green objects resembling leaves. He has large, green lips and a row of sharp teeth, and a red tongue. His rear is covered with his egg.
Peewee Piranha debuted in the game Super Mario Galaxy 2. In this game, he is the first boss fought, right before Mario meets Lubba and his crew. Peewee Piranha, when first encountered, is still unhatched in his egg, which is sitting on a bare planet with shreds of Dino Piranha's egg scattered in its atmosphere. However, the player lands on the top of the egg, cracking it a little and freeing Peewee Piranha. Peewee Piranha, enraged, screeched in anger as he broke out of his egg and rose up. Then, the battle begins. During the battle, Peewee Piranha crawls on its arms and legs, rapidly prancing around the planet and charing at Mario. To defeat him, Mario must attack his only weakness, his rear. To expose it, Mario must first spin at the egg by shaking the Wii Remote when he is right next to its surface. Every time Mario spins at the egg, Peewee Piranha will jump at him twice. After three spins at the egg, it will shatter, and Mario now must spin at his exposed rear. Peewee Piranha grows another egg, and the player must repeat the steps. After one more spin at his rear, Peewee Piranha will let out an anguished cry, and explode, revealing a Power Star.