Directed by: George Waggner
Starring: Claude Rains, Lon Chaney Jr., Ralph Bellamy, Warren William
Revealing mistake: When Larry is attacked by the werewolf, Bela, there are two shots when they are behind a tree, when he is actually fighting a man. (00:15:40)
Revealing mistake: When the wolf man is caught in a trap an falls on a log, his shirt opens at the fist and you can see that he is wearing hairy gloves. (00:17:54)
Continuity mistake: Early in the film, when the gypsy Bela becomes a wolf that attacks Jenny and bites Talbot, he is in true four-legged animal form, sans clothing. After being killed, his human corpse is wearing clothes although it is remarked that his feet are bare. Later, when Talbot transforms, he is a Wolf-Man, wearing clothes and walking on two legs.
Frank Andrews: I couldn't take my eyes off that walking stick of his.
Trivia: In Curt Siodmak's original script for the film, whether or not Lawrence Talbot really underwent a physical transformation to a werewolf or if the transformation simply occurred in his mind was left ambiguous. The Wolf Man was never to appear onscreen.
Question: At the time that this movie was made, nobody knew what made a werewolf, what could kill a werewolf, or when a werewolf would appear. Who decided that these things could happen?
Answer: Werewolves as a concept date back many years - this film originated many of the current conventions though, so the simple answer to your question is "the writers of this film". See the Wikipedia for more info - http://en.wikipedia.org/wiki/Werewolf.