Piranha Bean

The Piranha Bean is a Beanbean Kingdom sub-species of Piranha Plant that highly resembles a smaller version of Petey Piranha, except with the head of a normal Piranha Plant.

The Piranha Bean is one of the bosses in Mario & Luigi: Superstar Saga found near Beanbean Castle Town. It must be fought so the Mario Bros. could get a bean fruit which would get them the Beanstar piece in the Yoshi Theater, and Luigi must be separated from Mario to find it (which in the end, often leaves Luigi stronger than Mario because of the high experience it gives). While looking for Bean Fruits, Luigi found out that one of those had been swallowed by the Piranha Bean, and had to fight the irate plant so as to get it back.

During the battle, the Piranha Bean shoots small fireballs at the plumber. The boss can attack from various spots on the battlefield, which makes his attacks slightly harder to dodge. After the end, Luigi discovers that Prince Peasley too was swallowed by the Piranha Bean, and was shrunk to a very small size (the Piranha Bean itself sometimes uses the prince as a projectile during battle).

Piranha Bean might be a species, however it is unknown. If it's a species then Petey Piranha might be a Piranha Bean. This could explain the two Petey Piranhas in Mario Hoops 3-on-3 in Daisy Garden.

Trivia

 * Unlike most bosses, Piranha Bean's battle music was that of a normal fight with an enemy, though this was probably due to the fact that he only fought Luigi.