In the Japanese dub, Marlin is voiced by the comedian Noritake Kinashi, better known for many non-Japanese players as the creator and voice actor of Norimaro in Marvel Super Heroes vs. Street Fighter. Meanwhile, Dory was voiced by actress and essayist Shigeru Muroi.
In Spain, Anabel Alonso was well known at the time for her role in the Spanish sitcom series Siete Vidas (Seven Lives) and voiced Dory in the film. Curiously enough, Alonso is much more fondly remembered as Dory than in Siete Vidas to the point it almost angered fans when Alonso said she almost wouldn't appear in the sequel. Her co-stars Santi Rodríguez (Chum) and Blanca Portillo (Peach) appear as well. TV host and occasional actor Manel Fuentes voiced Nigel the pelican. Stage actor and singer Javier Gurruchaga has the double task of voicing both Bruce and Mr. Ray. José Luis Gil (Marlin), a veteran voice actor, had his live-action Star-Making Role that same year with Aquí no hay quien viva and was heavily promoted as a celebrity too. Ramón Langa (Gill) and Mercedes Sampietro (Coral) are also voice actors but they're recognizable faces too.
Creator Backlash: A minor one. While Albert Brooks enjoyed working on the film and by all accounts was pleasant to work with, he was frustrated by the fact that his voice was recorded in isolation, unlike The Simpsons, where he could ad lib off of the other actors. (Albert Brooks riffing with Ellen Degeneres is an admittedly awesome thought.)
Creator Couple: At some point after the film was released, José Luis Rivera, the Latin American Spanish voice of the swordfish talking about Marlin, would eventually marry Patricia Palestino, Dory's voice actress.
Creator Killer: Not to anyone at Pixar, but Disney boss Michael Eisner (erroneously) predicted this film would become Pixar's first Box Office Bomb, saying it would "take them down a notch". The film did the exact opposite and beat The Lion King out in gross AND became the highest selling DVD of all time, leaving an egg on Eisner's face and Pixar's employees in charge of any renewals to their contracts with Disney; their disdain for Eisner along with this film's success, among other factors, sunk Eisner's career at Disney, which allowed Pixar into the Mouse House fully (Pixar's first bomb wouldn't come for another 12 years, when The Good Dinosaur was released).
A deleted scene had Nemo making it through the sewage treatment plant. According to the DVD commentary, the director cut the scene for two reasons: First, it put too much more focus on Nemo- as Marlin is the main character of the film. Second, it didn't add anything that the rest of the movie hadn't already done; making it just a repeat of the filter scenes.
In a deleted scene, Nemo finds out Gill made up his backstory by looking at an illustrated book that a patient was reading on the dentist's chair.
Doing It for the Art: The DVD brags about how the animators recreated actual stock footage of the ocean as realistically as possible with their available tools to the point where the animated footage was deemed too realistic.
DVD Commentary: While the audiovisual commentary track was an interesting concept, by the time you get to the second or third behind the scenes segment interrupting the movie you can see why future films do not use the technique.
They do it better in the Blu-Ray edition of Toy Story 3, where the video actually stays in the frame in a picture-in-picture.
Enforced Method Acting: On her first take of Dory begging Marlin not to leave her, Ellen DeGeneres, already emotional from the scene itself, was so distraught from having thought she flubbed the line that she was crying by the second. The first ended up being used.
In Memoriam: For Glen McQueen, an animator who died of a heart attack a year prior, making this his last movie.
Inspiration for the Work: The inspiration for the film sprang from multiple experiences, going back to director Andrew Stanton's childhood, when he loved going to the dentist to see the fish tank, assuming that the fish were from the ocean and wanted to go home. In 1992, shortly after his son was born, he and his family took a trip to Six Flags Discovery Kingdom (which was called Marine World at the time). There, after seeing the shark tube and various exhibits, he felt that the underwater world could be done beautifully in computer animation. Later, in 1997, he took his son for a walk in the park, but realized that he was overprotecting him and lost an opportunity to have a father-son experience that day.
William H. Macy did a complete voiceover job as Marlin, but the brain trust felt the character needed someone more in line with Marlin's ever-manic and worrying personality, and recast the role with Albert Brooks. According to director Andrew Stanton, it "saved the movie".
Jess Harnell mentioned in a video where he talks about voices he provided for the Disney Theme Parks that he read for Crush before Andrew Stanton decided to do the character's voice.
Pet Fad Starter: After the release of this movie, kids wanted clownfish and others seen in the movie. Ironic, considering half the movie involves Nemo wanting to escape life in a tank.
Ellen Degeneres adlibed a lot of her lines as Dory, obviously.
Albert Brooks fell in love with the Deconstructionist aspect of Marlin - a clownfish who isn't funny - and ran with it. Director Andrew Stanton states "we have about an hour of audio from Albert telling a series of jokes really, really badly. They didn't make any sense, but that was the part that was funny.
Gil was going to lie to Nemo about his life in the sea in order to look more impressive. Nemo would then find out that Gil was lying when one of the patients starts reading a storybook about pirates that shared the exact same details. This subplot was cut because it made Gil too unlikeable.
The death of Nemo's mother was supposed to be slowly revealed in flashbacks, and was part of the initial structure of the movie, but was scrapped as the director felt that the audience would catch on what would happen fairly quick and thus, they would be stringing it out longer than necessary; starting the movie with her death would immediately justify Marlin's overprotective parenting. Reportedly, this plot structure was one of the reasons Michael Eisner felt Nemo would bring Pixar back to Earth. The idea of revealing the back story through flashbacks was used in the sequel Finding Dory.
In the concept art, Jacques was going to be a snail.
Crush was originally gonna sound more like an aging hippie.
Dory was originally intended to be a male character, but Andrew Stanton eventually changed the character to a female while watching an episode of Ellen.
William H. Macy was originally cast as Marlin, but his recordings apparently were TOO dramatic and not funny enough, so they made the choice to replace him with Brooks.
Due to Pixar not renewing its seven-film distribution deal with Disney in 2004 that would also give the latter full rights to its properties and sequel production, a sequel called Finding Nemo 2 was intended to be produced by a newly established studio called Circle 7 Animation, along with Toy Story 3 and a sequel to Monsters, Inc.. The plot would have involved Nemo and Marlin reuniting with another of Marlin's sons who survived the barracuda attack called Remy, only for Nemo to become jealous of Remy's newfound attention. Marlin would have gotten captured and sent to a marine-life institute (befriending a polar bear called Blanca in the process), forcing the two brothers to team up with Dory and a returning Gill to break into the institute and save their father. With the deal falling through in January 2006, and then-CEO Michael Eisner, who Pixar seriously disdained, getting ousted and being succeeded by Bob Iger, Disney would purchase Pixar and give creative control back to them, resulting in the sequel being scrapped. However, Finding Dory, produced in 2016, notably shares some plotlines (such as a character getting captured and taken to a marine-life institute and Dory having lived there during her childhood) with the scrapped sequel. Circle 7 would be shut down two months later, with most of the animators going to either the feature animation department or DisneyToon Studios.