Nemo

 is PJ's pet cat from Busted! In it, Nemo gets sick and PJ can't figure out what's wrong with him, so he gets Phineas and Ferb's help. However, this causes Perry to have to fight both Doofenshmirtz and Nemo's nemesis, Dr. Doofyblast.

Appearance
A black and white cat with a black nose and long, white whiskers.

Appearances

 * Busted! (First Appearance)