Litten (Nyabby in Japanese) is a quadruped, feline Pokémon covered with primarily black fur. There are two red stripes around each of its legs and two horizontal stripes with a vertical stripe across them on its forehead. The lower part of Litten's face is also red, and there is a large tuft of fur on each cheek. Its eyes are red with yellow sclera and it has short, pointed ears with pale gray insides. It has a short muzzle with a tiny, black nose. A tuft of fur sits at the end of its long tail. Litten's fur produces flammable oils. This allows it to collect fur while grooming, then use it form fireballs. When this Pokémon begins shedding, it burns all its fur in a blaze.
Litten is clearly based on a cat of some kind, possibly a Tiger (Panthera tigris tigris) based on it's stripes. It's color scheme, black body with yellow eyes, suggest that it might be a black cat (Felis catus). It's cheek tufts might be a reference to the Balkan Lynx (Lynx lynx balcanicus). The pattern on Litten's head is the alchemical symbol for Sulfur, a chemical element with the symbol S and the atomic number 16.
Litten's name may be a combination of lit, little, and kitten.
Nyabby may be a combination of ニャー nyā (meow), tabby, and 火 hi (fire).