- Acting for Two: Richard Greene plays both Sir Henry and Sir Hugo (even though Hugo is suppose to look like Stapleton the producers thought this would spoil the movie.)
- The 1981 Russian tv miniseries has the same actors who portray Jack Stapleton and Laura Lyons also portray Sir Hugo and his victim in the flashbacks.
- Billing Displacement: The 1939 film is the only Sherlock Holmes film where the actors playing Holmes and Watson did not get top billing. Richard Greene, the actor who played Sir Henry, got the top bill. Basil Rathbone got second billing and Nigel Bruce got fourth billing.
- Playing Against Type:
- Basil Rathbone was best known for playing villains before he was cast Holmes. Sadly however playing Holmes would doom Rathbone to typecasting again as he could never be associated with anything but Holmes after this.
- Christopher Lee in the 1959 version plays Sir Henry, a Nice Guy as opposed to his usual villainous self.
- Stillborn Franchise: The 1959 version was supposed to be the start of a series of films starring Peter Cushing as Sherlock Holmes. The film's disappointing box office returns dashed those hopes.
Trivia / The Hound of the Baskervilles