Muk

Muk is a massive sludge-like Pokemon and the evolved form of Grimer. Other than its gross sludge-like appearance, Muk is also known for its putrid smell. It is a living biohazard as it can kill plants wherever it goes.

There is an Alolan version of Muk that takes on a much more....colorful appearance. Its appearance came from its diet with garbage. Both Grimers and Muks were part of the solution to dealing with the region's garbage problem.