Ub Iwerks 

Ub Iwerks is credited with working laong side Walt Disney to create their most iconic character, Mickey Mouse. Iwerks was also the chief animator for "Silly Symphonies" and creator of oswald the lucky rabbit. Iwerk is credited for his work on developing xerographic and the mixing of live action and animation. The animator also won an academy award for his special effects work on Alfred Hitchcocks "The birds". While Iwerks is the creator  of Oswald the Lucky rabbit, he worked as Walt Disney's lead animator for many years.

Ub Iwerks was the lead animator for "Steamboat Willie".

Oswald the lucky rabbit 

Steamboat Willie