Cat

The cat is an animal that resides in the Earth Kingdom. It is a quadruped creature that is, unlike most of the fauna in the World of Avatar, a non-hybrid animal.

History
When Aang, Katara, and Sokka visited Omashu to do some sightseeing, the Avatar brought his friends on a ride down the city's delivery system. Once the cart had fallen off the rails and ruined countless buildings, a bearded cat jumped into Aang's wig which he had been using as a disguise, where the animal encountered Momo. The two animals fought with each other for a moment before the lemur pushed it out of the cart.

Aang later met another cat named Miyuki who was owned by a senile old woman. He had hoped that visiting the herbalist's medical institute might heed some sort of cure for Katara and Sokka's ailments, both of whom had caught a cold from a storm the day before. The herbalist boasted of her cat, Miyuki, who had grown to be ninety-seven in human years. Miyuki was alongside her owner when Zuko, Iroh, and June were led to the institute by Nyla, June's shirshu.

Fluffykins was a cat who resided in Ba Sing Se with a family. When Aang created a new zoo with his bending to replace the old, inhospitable one, Kenji, the zookeeper, complimented the Avatar on his accomplishment and suggested that he make a career for himself in animals. Kenji quickly retracted this opinion, however, when he overheard a few people, including Fluffykins' owners, finding their pets who had been mistakenly put in the zoo, as well.

Anatomy
The only cats that have been revealed were relatively small in comparison to other animals, and they vary greatly in type and color. Certain attributes that can change in cats are fur length, fur color, eye color, and body shape.

Tamed behavior
There have only been domesticated cats seen throughout Team Avatar's journeys. The bearded cat was quite hostile, although this may have only been because it felt provoked by Momo. Miyuki was was quite calm in all appearances, and Fluffykins did not have enough development for a personality to be distinguished.

They're tamed behaviors may depend on their breeds.

Connection
Every trait and outward appearance of cats in the series point to the idea that they are based simply on real-world domesticated house-cats.