First of all, Cait Sith the character ONLY appears in FFVII and he was, as someone has already mentioned, one of the most annoying and obnoxious characters in ANY Final Fantasy game. There is a Cait Sith doll in FFX, a costume in FFX-2, and some Cait Sith cards in FF Fables: Chocobo Tales
The reason why Final Fantasy USED to be a great franchise was because each game had its own unique identity and story. The only exceptions being the ubiquitous character named Cid who liked to tinker with things, crystals, airships, chocobos and a few of the summonable allies. Now all Final Fantasy means is, "How can we cross-reference as many themes/characters/plots/locations into our new games in order to rake in as much fanboy money as possible." In a consumer economy you vote with your money and I'm casting my vote for the Less Recyling, More Originality camp.