A carnivorous plant that lives inside green pipes, bobbing in and out on a set timer. It will not emerge if Mario is standing directly on top of or beside its pipe. Impossible to stomp — only fireballs or a shell can destroy it.
Hit it with a fireball as Fire Mario, or knock a Koopa shell into the pipe. You cannot stomp it. The safest strategy is simply to wait beside the pipe for it to retreat, then dash past.