Petey Piranha is a reoccuring villain in the Mario series. His first ever appearance was in Super Mario Sunshine.
Super Mario Sunshine
In Super Mario Sunshine, Petey appears in two missions on Bianco Hills. The first mission he is in you have to squirt water in his mouth when he tries to spit out gunk, causing him to swell so much that falls. When he falls his belly button will be sticking out and you must ground pound it three times. In the other mission you must squirt water in his mouth, waking him up. He will then fly around, and Mario must squirt water in his mouth so he falls and Mario then must ground pound him.
New Super Mario Bros.
In New Super Mario Bros., Petey Piranha is the final boss of World 5. Mario defeats by ground pounding him. If Mini Mario defeats him World 7 unlocks.
Mario Pinball Land
Petey Piranha appears in this games as the first boss. His appearance is slightly different in this game, with his neck longer and his mouth more outward.
Mario Party 10
Petey appears in Mario Party 10 as the boss of Mushroom Park, in the boss minigame, Petey's Bomb Battle. The contestants must throw bombs at him. He can swallow them and shoot the back.