They were introduced as an exotic alien race in the Trek animated series because the live action show didn't have the budget for them and the creators of Trek wanted to show that there were true "aliens" out there and not just people in makeup with pointy ears.
30 years later, a subculture of internet dwellers who have a sexual fetish for human/animal hybrids (and feel the need to impose them on everyestablishedfiction) have created an enormous fan following around Caitians, especially the female ones with long flowing hair.
[*] Caitians are gengineered Ferasans. For the transformation, Nepata leaves were used somehow. (Caitian Diaspora chain)
I got the impression that the Ferasans started manipulating there DNA and the Catians split off wanting no part of it.
I'll have to go read both sides of the chain again to be sure.
I was once DKnight1000, apparently I had taken my own name so now I'm DKnight0001. If I ask you a question it is not an insult but a genuine attempt to understand why. When I insult you I won't be discreet about it, I will be precise and to the point stupid.