Goomy looks like a light purple, vaguely slug-like pile of goo. The top half of its body is a lighter purple than its bottom half, and the two halves are separated by a squiggly, dark purple outline decorated with five green dots. It has beady eyes, and it has two rows of two horn-like structures on top of its head.
Goomy is widely considered the weakest Dragon-type Pokémon. Its body is made mostly of water. Once it dries out, it is unable to breathe and dies. Because of this, it hides in damp and shady places, such as swamps, to keep its body slimy. This slime is germ-laden, and makes punches and kicks aimed at it slide off harmlessly. It uses its sensitive horns to check out its surroundings. As seen in the anime, its diet consists of leaves.
Goomy greatly resembles the prehistoric wiwaxia. Goomy seems to be based on soft bodied gastropods, such as slugs and nudibranch; its typing and eventual dragon design in evolution may be a reference to the "blue dragon" sea slug. It may also be based upon the concept of living slime in popular culture.
Goomy may be a combination of goo and either gummy or slimy.
Numera is derived from 滑る numeru (to be slippery) and ぬらぬら nuranura (onomatopoetic word for slimy).