Piranha Plant

A Piranha Plant, known as Packun Flower (パックン フラワー, Pakkun Furawā) in Japan, is an enemy almost always portrayed as a leafy, green stalk topped with a white-spotted red or green globe and sharp teeth.

Appearance
Piranha Plants are large, carnivorous plants encountered throughout the Mario series; Piranha Plants are seemingly based-off Venus Flytraps, eating anything that approaches them. The head of a Piranha Plant is most commonly either red or green with multiple other colors. Originally, Piranha Plants were found exclusively in pipes, either darting-out and biting anything near or remaining still and spitting fireballs. Currently, Piranha Plants can be found both in and out of pipes and their fire-breathing ability is now rarely used﻿.

In Super Smash Flash 2
They may be one of the many enemies in the Adventure Mode stage Mushroom Kingdom. They appear in the begining of the level in a pipe trying to eat the player.