The evolution of Mickey Mouse’s appearance is interesting… but not nearly as interesting as his pre-history and the business and technical factors wrapped up in his development, as explored in this excellent video from 100 Years of Cinema:
This video includes footage of Walt Disney’s earliest animated mice from 1923, and gems like the following:
In 1927 Walt went into business with Universal Studios and started work on his first all-cartoon series: Oswald, the Lucky Rabbit. This was Walt’s first really successful cartoon, and after being paid five-hundred dollars per cartoon for a year, Walt wanted to renegotiate his contract for higher pay based on the success of the character that he’d created.
Universal responded by hiring away his animators, retaining the rights to his most successful character, and offering him a twenty-percent reduction in his salary.
Walt quit, and along with one loyal animator – Ub Iwerks – and immediately began production on a new character, this time one that he would own the rights to…
100 Years of Cinema – 1928: Steamboat Willie – The Surprising Origin of Mickey Mouse
Highly recommended.