Dory

Dory is the deuteragonist in Finding Nemo. She is a pacific regal tang.

Finding Nemo
She helps Marlin on his journey to rescue Nemo while heading to Sydney. She suffers from short-term memory-loss.

The friendly female can read and is very happy to have a companion. Marlin takes advantage of her short attention-span, but he later regrets it when it physically hurts her.

Dory never remembers Nemo's name. However, she does seem to care about the little fish.

Additionally, Dory comforts everybody she sees, like in the movie. The words ("There, there. It's all right. It'll be okay.") are used by Dory twice in the movie. Once when she first met Marlin, because she thought his head was hurting and again in the whale when Marlin was worried about Nemo. That being said, nearly at the end of the movie, after Nigel puts Marlin and Dory back in the ocean, a depressed Marlin barely kept his distance from Dory when she swam to him. After Dory tried so hard to comfort him, Marlin suggested that if Dory never took care of him along the way, he never would have even made it to Sydney. After Marlin leaves Dory meets Nemo who had escaped alive and at first she doesn't remember him but when she sees the word Sydney again all her memory comes back and she takes Nemo to his father. After finding help from some crabs, Dory and Nemo find Marlin, resulting in a happy reunion between Nemo and Marlin that is cut short when Dory gets trapped with a school of fish in a fisherman's net. Nemo rushes to help a distressed Dory, they tell the other fish to swim down together, and they all manage to escape the net.

At the conclusion of the film, Dory is seen to have become a latest member of Bruce's Fish are Friends Club as Bruce, Anchor, and Chum come over to drop Dory off. It is possible that she has become Marlin's new wife and Nemo's stepmother.

Trivia

 * According to director Andrew Stanton on the Audio Commentary for Finding Nemo DVD in the original story Dory was gonna be a male character but when Stanton went home to write the script his wife was watching The Ellen DeGeneres Show and he heard Ellen's voice and decided to change Dory to a female and casted Ellen in the role to which Ellen accepted the role.
 * Dory has cameoed in several of Boom! Studios' Disney comics including The Incredibles where she appears in an underwater scene, and Darkwing Duck, where she and other Disney sea creatures react in fear to the return of the villainous Paddywhack.