Nemo is a clownfish. It is funny, due to my species research, I can name just about every main fish on that movie.

Clownfish (nemo), Regal Tang (Dory), then the lesser main characters are Royal Gramma, Porcupinefish,
Yellow Tang, Humbug Damsel, Moorish idol, starfish (which is an invertabrate), butterfly fish, sea horse, etc. I probably missed afew but I haven't seen the movie this year so I can't remember everyone.
Ok, a little off topic, I am just glad to know that all the fish in finding nemo are real saltwater fish. (I don't think all the fish in the dentist's tank are compatable, I wouldn't try it.)
Unfortunately, the only peaceful fish (above) I can/want to keep in my tank is a clownfish (which are best kept in pairs). I love yellow tangs and Royal Grammas but they are highly aggressive.
Any suggestions will be appretiated! Thanks!