Piranha Plants are enemies from The Legend of Zelda: Link's Awakening. These enemies only appear in the side-scrolling platform areas of Koholint Island, and can be defeated with one sword strike, regardless of the currently equipped sword. Their only attack pattern is to rise from their pipes and return into them. Unlike some of their counterparts in the Mario series, they do not spit fireballs.
Piranha Plants are based upon enemies from the Super Mario Bros. series, first appearing in Super Mario Bros.. Piranha Plants appear along with enemies and characters from other Nintendo games. They are very similar to Deku Babas.
Interestingly, the Japanese manual for the original Legend of Zelda states that Testitart (Manhandla) is a giant Pakkun Flower (Piranha Plant).