Freddie Bartholomew was originally considered by MGM for the central dual role in 1935. However, real-life twins Billy Mauch and Robert J. Mauch were already under contract with Warner Bros, and they got the title roles.
MGM bought the rights to Mark Twain's novel in 1935 for $100,000, but never filmed the story. Eventually, Warner Bros. secured the rights.
This is the first of thirteen films in which Errol Flynn and Alan Hale would both appear. Several of them, such as The Adventures of Robin Hood (1938), The Sea Hawk (1940), Santa Fe Trail (1940), and Dodge City (1939), would feature them as friends, and not adversaries as they are in this film.
The Mauch twins, Billy Mauch and Robert J. Mauch, were born in 1921, making them fifteen when this film was shot. However the studio said they were born in 1924, and therefore many articles described them as being twelve at the time of filming. They were playing ten year olds.
Despite his top billing, Errol Flynn doesn't appear until the 52-minute mark. Some critics complained his entrance was too late in the film.