From https://www.mariowiki.com/Petey_Piranha --

"Petey Piranha is a large mutant Piranha Plant with a ring of petals on his head. His first appearance is in Super Mario Sunshine, and since then he has become a common and recurring boss in Mario titles. He consistently appears in sports games and spin-offs, and also features as a playable character in several sports games.

Petey Piranha was thought to be a loyal follower of Bowser, but this was undetermined until Mario & Luigi: Paper Jam showed Bowser directly giving him an order. It has been suggested by bios for Mario Superstar Baseball and Mario Party: Star Rush, as well as by his Japanese name, Boss Packun, that he is the ruler of his kind; "Packun Flower" is the Japanese name for the Piranha Plant.

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Petey has a different gender depending on the region. In English language versions, the Piranha Plant is male as his various bios refer to Petey Piranha as a "he" as well as in-game by a Pianta in Super Mario Sunshine, his first appearance. In French, however, Petey is female and her name is "Flora Piranha", derived from "Flora", a female name. In German, there seem to be inconsistencies about Petey's gender. For example, the plant is referred to as male in the trophy description of Super Smash Bros. Brawl, but is referred to as female in the character description of Mario Strikers Charged. In Italian, Petey is male, derived from Pipino, an uncommon Italian name. In Spanish, he is male in most games but female in New Play Control: Mario Power Tennis, sharing her French name. In the Japan-exclusive Super Mario-Kun, Petey is depicted as a female, a mother of several Piranha Plants.

In Paper Mario: Sticker Star, Kersti refers to Petey Piranha as an "it". His trophy in Super Smash Bros. Brawl also refers to him as an "it"."