erm actually only Fire Piranhas do that and in recent years they have evolved to be much more competent π€
Piranha Plants merely come in and out of their pipes, and the red-stemmed versions don't even stop if you stand on their pipes
there's also Frigid Piranhas, which spit homing iceballs at you
Putrid Piranhas, which breathe poisonous toxins at you
Ptooies, which suspend spike balls over themselves with their breath
Walking Piranhas, which, well, walk
Piranha Creepers
Pale Piranhas
Munchers
Nippers
and probably a lot more i forgot