Dory

Dory is the deuteragonist of Finding Nemo and the titular protagonist of its sequel Finding Dory. She is a blue-tang fish who suffers from short-term memory loss.

Biography
"Throughout the vast ocean you will not find a fish more hospitable, more friendly, and more sociable than Dory. 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."

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.

Despite her sunny outlook and demeanour, there is some tragedy to Dory. Because of her short term memory loss, there's no telling how many life experiences have eluded her, or how many loved ones she lost that she couldn't remember. When she starts travelling with Marlin, her memory starts improving, as indicated when she can repeat the address "P. Sherman, 42 Wallaby Way, Sydney". When Marlin thinks that Nemo is dead, and starts to go home, Dory doesn't want him to leave, because she is afraid that if she can no longer see him, then she'll forget everything. This fear is founded, as when the hopeless Marlin leaves her, not a few minutes afterwards her entire adventure has been (temporarily) wiped clean from her mind.

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 although only by blackmail of feeding them to seagulls, 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 Nemo's adoptive mother and a latest member of Bruce's Fish are Friends Club as Bruce, Anchor, and Chum come over to drop Dory off.