Muncher

Munchers ("Black Pakkun" in Japan) are an indestructible species of Piranha Plants. Unlike their white cousins, Muncher Plants come in black, depending on the location. They are almost completely invulnerable.

Super Mario Bros. 3
Munchers first appeared in Super Mario Bros. 3. They are first encountered in stage 6-9 of Iced Land where they appear in large numbers. Munchers can become frozen if hit with an Ice Block. Frozen Munchers can be identified by the black ice block in which they are encased (in contrast to yellow ice blocks, which hold coins). They are harmless when frozen and act like platforms, but if one thaws a Muncher out with a fireball, the Muncher will become active again. If Mario hits a P-Switch, then thaws a frozen Muncher in an ice block, the Muncher will turn into a coin, the only way to kill them.

Super Mario World
They appear again in Super Mario World, where they behave the same as in the previous game. In this game they can be walked on with the aid of a Yoshi.

Super Mario Land 3: Wario Land
They also appear in Super Mario Land 3: Wario Land. They are once again black and indestructible.

New Super Mario Bros. Wii
In New Super Mario Bros. Wii, Munchers appear in the level 9-7 where they are frozen in ice. They cover most of the floor and can be quite dangerous if the player(s) don't keep moving as there are several Venus Fire Traps in the level that can melt them. The player(s) can also melt them if they have a Fire Flower.

Characteristics and Traits
Munchers act much like spikes would, as touching them would damage Mario and Luigi. However, both the Kuribo's Shoe or any Yoshi can walk on them without harm. In a few levels, they spring from thin pipes. The only way to cross a patch of Munchers is by acquiring a Starman or by carefully jumping to the gaps between Muncher patches.

There is often confusion on what a Muncher exactly is. They are about the size of a Nipper Plant, but are firmly planted in the ground like a Piranha Plant. They also have eyes much like a Nipper Plant. They appear to be a sub-species and not part of the normal evolution chain of a Piranha Plant. In Super Mario All-Stars, these Super Mario Bros. 3 enemies were recolored, greatly resembling a Nipper Plant and not black like the classic Muncher.