Karrablast is a round, bipedal Pokémon with a primarily blue carapace that comprises a horn at the tip. Its black face has a teal patch on its forehead, a fanged mouth, and eyes with orange pupils and yellow sclerae. Its ridged underbelly, or plastron, is yellow, and its stubby arms and legs are black.
When it senses danger, it spews an acidic liquid from its mouth. It targets its rival Shelmet, so it can evolve through electrical-like energy. Shelmet is also the preferred prey of Karrablast, as it eats the inside after melting the shell. It resides in forests and fields, and it often hides in trees or grass if threatened.
Karrablast and Shelmet are the only Pokémon that have to be traded for a specific Pokémon to evolve, having to be traded for each other.
Karrablast's name, its capacity of producing corrosive substances as a method of protection, and its penchant for attacking Shelmet suggest it is inspired by a ground beetle. In an interview, Ken Sugimori confirmed that the original idea for Karrablast, as suggested by Atsuko Nishida, was a snail-eating beetle based on the Carabus smaragdinus species. Its horn, which may have also been inspired by rhinoceros beetles, somewhat resembles an escargot fork.
Karrablast and Shelmet's relationship may be a reference to coevolution, where the evolution of one species is influenced by changes in another species; in this case, the relationship between predator and prey.
Karrablast may be a combination of Carabus (genus of beetles belonging to the ground beetle family), κέρατο kérato (Greek for horn), or carapace (the upper half of a shell, which is commonly, albeit incorrectly, associated with beetles), and blast (referring to its defense mechanism) or plastron (French for chestplate). It may also be derived from Carabus blaptoides, a species of ground beetle endemic to Japan.
Kaburumo may be derived from 蝸牛被 maimaikaburi (Carabus blaptoides) and 甲虫 kabutomushi (beetle).