Wanted to become an engineer as a child
Was hearing-impaired since 1918, when he was in Germany fighting the war.
Was named the 21st Greatest Actor on The 50 Greatest Screen Legends List by the American Film Institute
Was voted the 7th Greatest Director of all time by Entertainment Weekly, making him the highest rated comedy director. Charles Chaplin didn't make the list.
When he married Natalie Talmadge, the Talmadge family was one of the great acting dynasties in both theater and film, and the gossip in Hollywood was that Keaton married her to gain respect in the industry, a rumor he never quite lived down during his peak. Ironically, Keaton is now a film legend, while most people would be hard-pressed to answer who the Talmadges are.
When he was three years old, he got his right index finger caught in a clothes wringer and it was crushed and had to be amputated at the first knuckle. The injury is most clearly visible in The Garage (1920), when Keaton steadies Roscoe 'Fatty' Arbuckle's head with his right hand while wiping oil off his face with his left.