Initially Walt Disney was uninterested in making this movie. To get him interested, story men Joe Grant and Dick Huemer wrote up the film as installments which they left on Walt's desk every morning. Finally, he ran into the story department saying, "This is great! What happens next?"
Cels for "Dumbo" are the rarest in the industry. The animators, after the scene was safely "in the can", would strew the used cels in the corridors and go sliding on them. In addition the gray paint (used for so many of the elephant skins) would "pop" when the cel was flexed. Many irreplaceable cels were destroyed this way.
A very tightly budgeted, scripted, and produced film, because Walt Disney needed the film to bring in much-needed revenue after the expensive failures of Pinocchio (1940) and Fantasia (1940). Final negative cost of Dumbo was $813,000 (making it the least expensive of all Disney's animated features), and it grossed over $2.5 million in its original release (more than Pinocchio's and Fantasia's original grosses combined).
While trying to comfort Dumbo, Timothy says, "Lots of people with big ears are famous!" According to animation historian John Canemaker on the 2001 DVD release commentary, the line was recognized by audiences of 1941 as a reference to Clark Gable. The line was also featured in the original theatrical trailer.
During production there was a long and bitter animators strike, in which half of the studio's staff walked out. Some of the strikers are caricatured as the clowns who go to "hit the big boss for a raise".
"Dumbo" was the first Walt Disney Animated Classic to be released on videocassette. Its first video release was in 1981 for rental only, and put on sale in the summer of 1982. It was then repackaged in 1985 and 1989 and again in 1994. Then it was first released on DVD in 2001 and again in 2006, and the newest release in 2011. Dumbo has never gone out of print, thus considered the longest Disney animated feature on video to be in print since it came out.
HIDDEN MICKEY: When the drunken Timothy is sliding down the staircase-shaped bubble Dumbo has blown, his laugh is actually that of Mickey Mouse. Also, when Timothy coughs on Jim Crow's cigar smoke, that cough is also that of Mickey (it was specifically heard in both Giantland (1933) and Two-Gun Mickey (1934)).
There's a reference to "The Little Engine That Could". While Casey Jr. is trying to get up a hill, the train sounds like it's talking. It says "I think I can, I think I can." Then when the train gets up the hill and starts going faster, it changes to, "I thought I could, I thought I could."
Walt Disney's distributor, RKO Radio Pictures, had qualms about releasing this 64-minute feature as a major motion picture. They tried to persuade Disney to either cut it to short-subject length, extend it to at least 70 minutes, or have it released as a B picture. Disney stood his ground, and the film was released as an A picture as Disney intended.
A sequel direct to video/DVD titled Dumbo 2 was announced back in the early 2000s. With a story that takes place after the original involving Dumbo and a group of young circus animals to get separated from the WDP Circus and try to find their way back to the circus. This proposed idea appeared to have been canceled with no more than storyboards and animated drawing sheets being made during preproduction.
During the song "Look Out For Mister Stork" the lyrics state, "Remember those quintuplets and the woman in the shoe." The latter is of course in reference to the classic nursery rhyme "The Old Woman In The Shoe". The former is a reference to The Dionne Quintuplets from North Bay, Ontario, Canada. The Dionne Sisters were well-known for having been the first complete set of quintuplets to survive birth, where many multiple-child births of the time were more fatal. The Dionnes were often exploited to the public before finally being reunited with their family.
The "Casey Junior" segment was originally much longer. It was drawn and animated, then heavily edited, cutting several minutes from its run time. The full length segment can be seen on Disney's The Reluctant Dragon (1941) DVD.
One of the crows calls Timothy Mouse "brother rat." This is the traditional name for cadets at Virginia Military Institute, an group which adopted the name for themselves in the 1850s after rich folk used it as a pejorative against them, describing their shabby, "ratty" uniforms.