Spencer joined Walt Disney Productions in 1931 and first worked on several early Mickey Mouse cartoons. In 1932 he began independently producing a two-tier Mickey Mouse comic strip, even though he was not connected with the comics department at Disney. The studio approved the project and the strip appeared in the national DeMolay newsletter. The character Donald Duck was introduced at Disney in 1934, and Spencer began to focus more on Donald than on Mickey. In 1935 Spencer wrote an analysis of Donald which served as the standard for writing for, drawing, and animating the character. Spencer's model sheets included in the report feature a redesigned version of Donald that was shorter and rounder – largely identical to his appearance today. Spencer also included remarks on Donald's personality and mannerisms. Spencer animated on seven Disney short films as well as the studio's first feature, Snow White and the Seven Dwarfs (1937). Spencer's short projects include Mickey's Fire Brigade (1935), On Ice,Moving Day (1936), Donald and Pluto, Don Donald (1937), Pluto's Quin-puplets, and Donald's Golf Game (1938). -From Wikipedia
