Walt Disney
Walt Disney, the sweet, mild-mannered inventor of Mickey Mouse and an assortment of other characters who made our childhoods wonderful, actually served in the US military in both World Wars. He fooled recruiters by altering his birth certificate to meet the age requirement, and later worked as a driver for the American Red Cross Ambulance Corps.
During World War II, he was tasked with creating propaganda cartoons and educational videos, putting his artistic abilities to good use. This was the foreshadowing of his long and illustrious career. His task was unheard of at the time, so the army created a unique unit for it called the Walt Disney Training Films Unit.