Walt Disney physical performance as Mickey Mouse (lost animation reference footage; late 1930s)
Mickey Mouse in The Pointer from the scene in question and Walt Disney, who wore his felt hat for this performance.
There does not seem to be any need to introduce animator/businessman/producer Walt Disney. The man behind the most famous entertainment company in the world, his most known creation is the cartoon character Mickey Mouse that he also personally voiced in his early appearances.
What is lesser known, though, is that Walt Disney was once filmed physically performing as Mickey Mouse so as to be used as reference footage by his studio's animators.
The 1939 Mickey Mouse animated short The Pointer is the cartoon for which Walt Disney physically performed as animation reference.
The Pointer is also notable for having the first "modern" design of Mickey with his eyes having defined white sclerae and a peach-toned face (which would be popularized in the 1940 animated feature Fantasia).
Walt Disney was very enthusiastic when he'd talk about a cartoon he would ask his team to work on, often moving and acting the characters' personalities and mannerisms. When he described The Pointer, he would physically emulate how Mickey would act when facing a bear. The animation team found him "so funny acting out [his] confusion that [they] asked if [they] could shoot a film of him as he recorded the lines."
Disney reluctantly agreed, but only if the camera was far away and without the animators looking like they were staring at him, as he was understandably embarrassed.
The camera was so far away that Disney was reduced to a tiny figure on film, but his performance, dressed in baggy clothes and his felt hat, was strong enough to use as a good reference for the cartoon's scene. Notably, when Disney was on stage, he instinctively indicated with his hand that Mickey Mouse was the size of a small child.
Disney refused to ever repeat the experience, and when the animators tried to look for the footage film years later, it was gone, without explanation. To this day, it is still lost.
- Disney Animation: The Illusion of Life - 1981