One of the greatest animated shorts ever! If you aspire to be an animator, you must watch and study this film.
Here's some general foreground of this film. During this time, Walt was very busy making Snow White and the Seven Dwarfs. However, in order to create special effects in Snow White in the way Walt envisioned them, the animators had to run tests. They had to see if these effects were even possible and they wanted to see the audiences reactions.
Walt wanted Snow White to be as lifelike as possible so the audience would observe the movie as a live action film rather then a cartoon. Unfortunately, animation is in 2D so Walt and his staff came up with a solution called "The Multiplane Camera" which gave animation a 3D effect.
Different uses of lightning, color, and realism in animals was experimented in this film.
Walt won an Oscar for this film and totally deserved it.