Mickey Mouse did not first appear in Steamboat Willie, contrary to popular belief. Steamboat Willie was actually the third animation Mickey appeared in.

Using Oswald the Lucky Rabbit as a starting point, Walt created Mickey Mouse, basing it on Oswald's character design and a real mouse that used to share Walt's tiny studio shack when he was starting out in Kansas City. Mickey was originally named Mortimer. The Disney studio produced the first short of Mickey called Plane Crazy, which coincided with Charles Lindburgh's crossing of the Atlantic in an aeroplane. Ub Iwerks, the uberlegendary animator who teamed with Walt Disney, was known as the fastest animator on the planet. He proved his worthiness of that title by producing 700 drawings for the film in one day, averaging an astounding one drawing per minute. Mickey's second film was called Gallopin' Gaucho. Walt headed out to New York City to find a distributor for these two animations with his new star character.

After the release of The Jazz Singer, the first talking movie, Walt Disney decided to bring sound to the animation genre. While he was in New York, he stopped production on Mickey's third film, Steamboat Willie, to have the studio do something unheard of - he wanted them add sound to the animation.

When he returned to the studios, they began brainstorming ideas. Wilfred Jackson, one of the Disney animators, suggested that rhythm and sound effects could be matched to the animation frames. Since there were 24 frames per second, music could be added and the animation matched to it using multiples of 8. They released Steamboat Willie to an amazed nation, and received standing ovations, rave reviews in the New York Times, and a good chunk of capital that was used to create the Disney empire.