Marlin
Nemo's father. Very scared and to himself until his son goes missing. Marlin is usually the one talking AT Nemo instead of WITH Nemo. He is an introvert.
Nemo
Marlin's son. Nemo defies his father and goes out to sea to touch a boat and gets taken. He doesn't listen to his father because his father smothers him and talks AT him. Nemo is a pretty good balance between intro- and extrovert.
Dory
A lone fish in the sea. She has short term memory loss until she meets Marlin and slightly remembers things. Dory is VERY verbal with EVERYONE. She is the life of the party. Dory is an extrovert.
Squirt
Crush's son. He is very relaxed and chill as Crush would say. He is pretty independent. Squirt is an extrovert.
Crush
Squirt's father. He is very chill and relaxed like his son. Crush is an extrovert. He is like his son's best friend, not like the relationship Marlin and Nemo have.
Bruce
Comes off as evil but he isn't. Bruce apparently has had issues with his father. In the movie it is stated, "he never really knew his father." I would say he is a good balance between intro- and extrovert.
Gill
He is almost like Nemo's second dad. While Nemo was taken, Gill looked over him. Gill is an introvert and definitely a loner. He has clearly been hurt and I think that has shaped him as a fish.
Nigel
This character is hilarious. He plays a big part in "Finding Nemo" because he is the one who gets Marlin and Dory to Nemo at the dentists office in Sydney.
Deb/Flo
This is an interesting character. She is not aware that she doesn't have a sister. She thinks her reflection in the tank is her "sister." Deb/Flo is an extrovert with a loud personality.
Peach
This character isn't too significant in the movie besides telling everyone in the tank if the dentist or his niece is coming into the room while they try to escape.
Gurgle
He is a complete germaphobic. If the tank gets dirty he freaks out. Slightly OCD.
Bubbles
Bubbles like to chase these bubbles that come out of the treasure chest in the tank. Every time it pops open bubbles come out. That's how he got his name. He is a little bit of an airhead.
Jacques
He cleans everything in the tank. Gurgle loves this character since he is a germaphobic.
Bloat
He is a frightened character. Every time he gets scared he blows up since he is a blowfish.