Catkind had some similarity to the non-humanoid cats of Earth, though they were closer to the size of a human. They had fur in a variety of lengths and colours, including brown, black and tabby stripes. (TV: Gridlock) They also had retractable claws which they could use for defence. (TV: New Earth) However, though physically similar to Earth felines, they were different in internal anatomy. (COMIC: Agent Provocateur)
Catkind reproduced in their teenage years, and often had litters of several kittens. They could also reproduce with humans. The offspring would look just like kittens of conventional Earth house cats, though capable of speech. (TV: Gridlock)
Catkind could live for at least thirty years. Novice Hame, a member of the Sisters of Plenitude, was young in the year 5,000,000,023 at the time of the order's dissolution, and lived beyond the Face of Boe's death in 5,000,000,053. (TV: New Earth, Gridlock)
Circa 4,999,999,740, Catkind lived on the planet New Savannah. They were a primitive people at the time, and their natural resources were running low. The New Earth Empire came to New Savannah, and brought it and Catkind into the empire. They agreed to give the Cats autonomy until the year 5,000,000,000, when control would be given to the New Earth Empire. Within fifty years, Catkind had reached the same level of technology as the humans, and Catkind grew to distrust them. In order to avert a potential war, they left the Earth empire cities, which were then covered by empathic force fields, stopping any Cats from returning. Myths would spring up about these Cats, specifically about them being angry spirits.
In the intervening centuries, a cult sprang up to oppose human influence. With the help of Bubastion, they destroyed the headquarters of Vedela Defense Systems, which controlled the force fields around the city. At the stroke of midnight at the start of 5,000,000,000, the force fields were shut down and gigantic robots, disguised as undead Catkind, entered to the city. Unfortunately, Bubastion had programmed them to attack everyone, intending to use New Savannah for his own purposes. When Garrard Townsend, a member of the cult, learned they were being used, he turned the force fields back on and deactivated the robots. (COMIC: Agent Provocateur)
In the year 5,000,000,023, the Sisters of Plenitude ran a hospital near New New York on New Earth. They had cures for nearly every known ailment and were able to heal their patients at a remarkable success rate. Unfortunately, these amazing skills were gained by using thousands and thousands of grown human clones known as "the Flesh". They were infected with every known disease and culled when any began to show sentience. These disease carriers were released by Lady Cassandra and cured by the Tenth Doctor, producing the new humans. The Sisters were arrested by the NNYPD for their crimes. (TV: New Earth)