Cait Sith, who appears to be a cute kitty on a stuffed mog with wings, is more than he appears. You'll find out much, much more about him later in the game...
Like Barret, Cait Sith's HP is much more significant than everyone elses. I don't recommend to play with him that much, but just because his M-phones are hard to get, especially his stronger ones.
Cait Sith's Limit Breaks
Cait Sith's Weapons