Fake Russian: Fievel's voice actor wasn't even remotely Russian, and neither was Tanya's. And Papa's voice actor, Nehemiah Persoff, was born in Tel Aviv, Israel (then Palestine). Though he and Fievel's voice actor Phillip Glasser were Jewish, so they were halfway there.
Mama's voice actresses (Erica Yohn, Susan Silo, and Jane Singer) play this trope straight, not to mention Lloyd Battista and Pat Parris respectively as Papa and his kid sister Sophie on the TV series.
Fake Nationality: Christopher Plummer plays a French pigeon, as well. And Gerrit Graham voices the British-sounding Cat R. Waul on the TV series.
Averted in the Latin American Spanish dubs, since he was voiced by male voice actors using a younger voice.
Cut Song: Fievel was supposed to have another song in the sweatshop.
The Danza: It's quite possible that Fievel's nickname 'Philly' was chosen because of the name of his voice actor, Phillip Glasser. Although since Steven Spielberg's grandfather was also named Fievel but renamed Phillip in America, it could have just been a very fitting coincidence.
Dueling Movies: An American Tail and The Great Mouse Detective. (Sort of; that movie came out in the summer, while Tail was released for the Thanksgiving/Christmas holiday season, though things were tense as Disney watched how well Tail would do in comparison to Detective.) An American Tail won and became the highest grossing animated film in history up to that point, but unfortunately, like The Sword in the Stone and Robin Hood, it struggled to get critical acclaim on its initial release. Regardless of this film beating Great Mouse Detective, the latter film was sufficiently successful both critically and financially to regain the confidence and save Disney from going bankrupt, while the success of An American Tail boosted the careers of Don Bluth and Steven Spielberg, forming an Amblin Entertainment Studios. It was a tie.
Executive Meddling: This film and The Land Before Time were the only examples of this notbeing a bad thing for Bluth. Creatively, it was always Spielberg's word over his, which he was not happy about, but then again, it wasSteven Spielberg, although Bluth claims that Spielberg at least gave him the space to do his job properly. Both parties, however, were victim to Universal's lack of funding, as the higher-ups had no way of knowing whether or not it would be successful, resulting in several unfinished scenes and a somewhat choppy plot. Spielberg, who had never worked in animation before, was also frustrated by how notoriously slow and expensive it was to create even a single scene.
The studio was concerned that kids wouldnt be able to remember Fievels name, and asked to make it something more familiar to Americans. This also ended up being a good thing, as they agreed to a compromise where Fievel would be nicknamed Philly, in reference to the real practice at the time of immigrants having their names Anglicized, and left it up to the kids themselves which name he would be popularly known by, with the original winning out.
When David Kirschner came up with the idea for this, it was originally intended to be a half-hour television special, but thought it would be better as a full-length animated feature. He decided to turn to Disney, but the studio turned it down on the grounds that a story about a Jewish mouse was not commercial, leading to Kirschner relying on Steven Spielberg and Disney exile Don Bluth to make the magic happen. One wonders how much of an impact it would have made for pre-Little Mermaid Disney if they actually trusted the audience enough in not feeling alienated by the hero's religion!
The movie's plot was originally meant to be a flashback story told by 107-year-old Fievel to his great grandkids in present day. The likely reason the idea was scrapped is because it felt really unnecessary. There's also the utter impossibility of a mouse becoming a centenarian (and even if Fievel aged like a human, he'd be close to the equivalent of one of the world's oldest; not impossible, but not very believable) note It does happen in the book adaptation, though. Also, one wonders if this idea was not ripped off in The Legend of the Titanic, also starting off with an old mouse recounting an event when he was young to his family.
Fievel's nickname "Philly" wasn't in the original script (and therefore, neither was the Chekhov's Gun of Tanya's name being changed to Tilly when the Mousekewitz's arrive in New York City- after all, "if it's not essential don't include it in the story".) The nickname was added because Bluth thought that "Fievel" sounded too foreign, and audiences wouldn't like it," so Spielberg and Bluth agreed to have him be called "Fievel" by his family, but "Philly" by everyone else. Bluth was ultimately proven wrong.
In the original script, Gussy was going to make an announce that Fievel was looking for his family at the big meeting of all the New York mice to discuss what to do about the cat problems (besides paying Warren T. Rat for no protection''). Unfortunately, Fievel's family was sitting in the very back and when Gussy announced Fievel's name, a ship horn drowned it out for them. It might have been cut because of how unneccesarily cruel it seemed.
Jerry Goldsmith was considered to compose the score, but was too busy with other projects and was replaced by James Horner. Had things turned out differently, it would have been the second collaboration between Bluth and Goldsmith, after The Secret of NIMH.