California, Here I Come:
October 16, 1923 was the start of Disney Brothers Studio, Roy and Walt, it was later renamed to The Walt Disney Studio.
After four years of Alice, he created Oswald the Lucky Rabbit. Twenty-six Oswald cartoons later, Disney learned a hard lesson when the distributor decided to produce the animated films on his own. From that point on Walt owned everything that he made.
Mortimer Mouse, Make that Mickey Mouse Was Born:
We’ve all heard the story of how Walt’s wife Lilly preferred Mickey over Mortimer, so he was renamed Mickey Mouse.
Ub Iwerks animated the cartoons, but with the advent of sound in films Walt decided to make the first sound cartoon Steam Boat Willie, even though the first two Mickey films had not yet been released. The film was released on November 18, 1928.
And the Rest is History:
In Walt Disney - Multiplane Camera, it's mentioned "Mickey Mouse’s image is the most reproduced in the world. "Over 7,500 items bear his likeness. Jesus is number two, and Elvis is number three". The first licensed item is reported to be a 1929 children's school tablet.*
Although many of the early Mickey Mouse items have a more pronounced nose, you can see by the 1929 United States Patent that Mickey looks exactly the same as he does today. Mickey hasn't aged a bit.
*Official Price Guide to Disney Collectibles by Ted Hake