From the NeoAnime Laws of Japanese Animation
#27 - Law of Feline Mutation
Any half-cat/half-human mutation will invariably:
1) be female
2) will possess ears and sometimes a tail as a genetic mutation
3) wear as little clothing as possible, if any.
In addition, the mutation varies highly from specimen to specimen. Some are covered completely in fur, some have fur striping, some have little or no fur at all (aside from ears and tail). Some display enhanced balance and reflexes, some do not.
Famous nekomimi include Felicia from Darkstalkers, Eriya, Naria, and Merle from Escaflowne, Nuku Nuku from All Purpose Cultural Cat Girl Nuku-Nuku, Kitty N from Bust a Groove, Pink from Dragon Pink (hentai), Anna Puna and Uni Puma from Dominion, Tin Nyanko from Sailor Moon... The list goes on and on. =^_^=