Based on the book by Helen Aberson and Harold Pearl, and adapted for the screen by Joe Grant and Dick Huemer, Dumbo was Disney's fourth feature film. And it kind of saved the studio after the poor reception of Fantasia and even Pinocchio.
Even though the movie runs only 65 minutes and had a budget three times smaller than previous feature films form Disney, Dumbo works on the characters' great personalities and awesome animation.
The look of the movie is very cartoony, more in the style of the Silly Symphonies than the three previous films. If you look at the animation, there is so much exaggeration and life to every scene. Just take Casey Jr (the Circus Train) for instance. He only appears for a really short time in the movie, but he's got such a defined personality that those few moments when we see him are really great.
Even Dumbo is a great example of great animation and character development. Throughout the movie, he doesn't say even one word, but the emotion that we get from him is huge. And the credit for this great performance goes to Bill Tytla, who in the past had animated characters such as Stromboli and Chernabog, and had a tallent for animating powerful characters.
Using live action references for animation had become very popular in the studio, and for this film one of the most rare references was used. A dance group called Jackson Brothers was responsible for coming up with the great choreography used by the crows.
This is one of Disney's more emotional films, we have great gags, but also some really moving scenes that could almost make us cry. Even Grant and Huemer warned Walt Disney that, if he considered himself as a fainthearted person, he should not keep reading the script (which they presented to Walt one chapter at a time, instead of giving him the whole thing).
The film was completed just before the Disney animators strike began, and was a huge success even when it was released two weeks before the attacks on Pearl Harbor (Dumbo was set to appear on the cover of Time Magazine, but the image was replaced by an illustration of Yamamoto).