Muk is a large, sticky, amorphous Pokémon, made of living purple sludge. It has two small eyes with beady black pupils. It also has an enormous mouth with a grey tongue and strands of ooze connecting its top and bottom jaws. While it has no visible legs, it does have two arms with three fingers on each hand. However, it typically keeps one hand tucked in while it extends the other hand.
It is a living biohazard, leaking toxins that instantly kill all plant life it touches. Even it being in close proximity to plants will cause them to wilt and die. Extreme caution is advised in avoiding any contact with this Pokémon, as an accidental brush up can lead to severe sickness. The effects of this Pokémon can leave the landscape barren for three years.
In dirty residential areas where people throw trash into the streets, it is almost certain to appear. It will readily consume nearly any waste or refuse generated by people and Pokémon alike. It can be found in heavily polluted bodies of water, cities and factories.
From Muk's body seeps a foul fluid that gives off a nose-bendingly horrible stench. Just one drop of this Pokémon's body fluid can turn a pool stagnant and rancid.
This Pokémon's favorite food is anything that is repugnantly filthy. In dirty towns where people think nothing of throwing away litter on the streets, Muk are certain to gather.
Although Muk's body is very poisonous, it doesn't seem to harm Ash and the others when Muk is 'hugging' them. This is probably because it is able to control whether it gives off poison or not, similar to how Ponyta can choose whether or not to burn the person that touches it. Croagunk is another Pokémon which is able to control the amount of poison it uses via its fingertips when using Poison Jab, or Sharpedo activating its Ability, Rough Skin.
Muk is tied with Mew for the shortest English name out of all Pokémon.
Muk shares similar traits to Weezing and Garbodor. All three Pokémon are pure Poison types with a single pre-evolution, roughly the same base stat totals and evolution levels, and appear to be based on a different kind of pollution; Muk being water pollution.
Origin
It appears to be a pile of living sludge. Muk may also be based on the imagined fear that heavy pollution, caused by the leakage and/or improper disposal of toxic/radioactive waste, may result in the creation of new and undesirable life.
Name origin
Muk is a corruption of muck (generally something filthy).
Betbeton may be derived from べとべと betobeto (sticky).
This Pokémon article is part of Project Pokédex, a Bulbapedia project that aims to write comprehensive articles on each Pokémon species, as well as Pokémon groups and forms.