Petey Piranha is a character introduced to the Mario Kart series in Mario Kart: Double Dash!!. Roy Koopa is considered the leader of the Piranha Plants that appear in many of the games in the Mario series. Petey Piranha is a boss in New Super Mario Bros., Super Smash Bros. Brawl, and Super Mario Sunshine. Petey is a heavyweight character, meaning that his choice of karts tends to have a high top speed and traction, but poor acceleration and handling. In Double Dash!!, his default kart is the Piranha Pipes and his default partner is King Boo. He can use any Special Item, along with King Boo. Win the Mirror Star Cup to get him.
Petey Piranha is one lucky Piranha Plant. Instead of popping in and out of a green pipe, he gets the opportunity to roam free on his spiky, green legs (although he prefers to drive in Mario Kart). His chest is dotted with dark green spots, and sharp, spiny leaves serve as his arms. His head is huge compared to his body, and it is red with white dots speckled on it. Yellow petals outlined in orange surround his head. He has big green lips, and his teeth are extra deadly and sharper than an ordinary Piranha Plant. His only article of clothing is a pair of red and white dotted underwear. No one knows why he likes that pair of underwear so much, but some guess he wears them because they make him look amazingly trendy. Amazingly.
- Petey is the only character tall enough to be able to get hit by the roller coaster in Baby Park.
- Petey was going to be in Mario Kart Wii, but was scrapped for unknown reasons.
- In Mario Kart Wii, the Kart, Piranha Prowler is modeled after him.
- In Mario Kart: Double Dash!! he, along with King Boo, can use every racer's special item.