Marlin is the main protagonist (main character) in the Disney/Pixar 2003 film Finding Nemo .
Marlin is a clownfish who makes his home inside a sea anemone in the Great Barrier Reef. He once had a wife Coral who died in a barracuda attack, along with almost all of his children. Also as a result of the attack, he has one son, Nemo.
Marlin can be somewhat overprotective of Nemo. He also tends to be neurotic, worrisome and pessimistic believing Nemo can't swim well when he actually can. However, this does not stop him from going on a journey to find his lost son, proving his determination.
Inspiration for Marlin's character came from Sebastian ("The Little Mermaid") and Geppetto ("Pinocchio")
Marlin is the #17 greatest Disney Hero. Ultimate Disney.com
Source: Marlin
Dory is the deuteragonist (second most important character) in the Disney/Pixar 2003 film Finding Nemo,
Throughout the vast ocean you will not find a fish more hospitable, more friendly, and more sociable than Dory, a Pacific regal blue tang. She would love to chat with you all day and tell you her life story... but she can't. Dory suffers from short term memory loss. Dory is the aquatic Good Samaritan who offers to help Marlin on his journey to find his son. She is certainly an odd partner for such a quest, but her optimism proves an invaluable quality to help overcome the impossible. To Dory, the glass is always half-full.
Dory is a very optimistic, kind, ditzy but forgetful fish. This is due to the fact that she suffers from short term memory loss, which is implied to have frustrated her friends and family to the point that they left her.
Dory is the #17 greatest Disney sidekick. M-magazine
Source: Dory