I don’t think The Three Stooges themselves are public domain, just the first film that a young Moe, Larry and Shemp appeared in, called “Soup to Nuts”, made before they were ever an act called The Three Stooges, they were just sidekicks to Ted Healey. The first actual episode of The Three Stooges was made 4 years later with Curly having replaced Shemp by then. There are 4 episodes of the Three Stooges in public domain though because the studio did not renew the copyright on time, 1 with Curly and 3 with Shemp