Meowstic is a bipedal, feline Pokémon whose appearance differs drastically between genders. Both genders have two tails, folded ears, a small collar of fur around the neck, and a tuft of fur on top of the head.
The male Meowstic is predominantly dark blue. Its eyes are green with light blue sclerae. The tuft of fur between its ears is white and curves slightly to the side and the collar around its neck is white with several stray tufts of fur. It has pointed ears with white at the fold and on the tips of its ears; there is also a white ring near the tips of its ears. Its tails are also pointed with white tips and a white ring near the end. There is a tuft of fur on each hip and it has white paws. The female Meowstic is predominantly white. Its ears have no markings and curled tips and its eyes are red with yellow sclerae. The tuft of fur on its head is blue and curled, as is the collar around its neck. Its tails are blue at the base and end in white, fluffy curls. There are blue, stocking-like markings around its paws and two tufts of fur on each hip.
The eye-like organs hidden under the fold of Meowstic's ears emit psychic energy powerful enough to obliterate a 10-ton truck. It usually keeps its ears folded in order to keep this power in check, but it will unleash this power if threatened.
Meowstic is the only Pokémon to have separate movesets for each gender.
During Google's April Fools' Day 2014 event, Meowstic's genders had separate Dex numbers in Google's regional Dex. The male was #139, while the female was #140.
Meowstic may be based on the domesticated variety of nekomata, a cat yōkai that comes from a domesticated cat who lives many years until its tail splits and it gains supernatural powers, much like how Meowstic evolves from Espurr. Nekomata were often depicted as standing on two legs like a human, and in at least one account shown to be wearing handkerchiefs on their heads, similar to Meowstic.
It could also be based on the very similar bakeneko. In addition, its folded ears are similar to the Scottish Fold breed of cat.
Meowstic is a combination of meow and mystic. It may also derive from stoic, referring to its generally emotionless facial expression.
Nyaonix may be a combination of ニャー nyā or ニャーオ nyāo (meow) and onyx or ὄνυξ ónyx (Greek for claw), psionics, or the Greek goddess Nyx (goddess of the night, associated with magic).