Gwynplaine's fixed grin and disturbing clown-like appearance was a key inspiration for comic book writer Bill Finger and artists Bob Kane and Jerry Robinson in creating one of the most iconic comic book villains ever, The Joker, archenemy of Batman from DC Comics.
Gwynplaine's grotesque grin was achieved with prosthesis. Conrad Veidt was fitted with a set of dentures that had metal hooks to pull back the corners of his mouth. He couldn't speak when the dentures were in. The only scene in which he did not wear the prosthesis is the scene where he is ravished by the Duchess Josiana.
One reason the studio opted to make the film is because the works of Victor Hugo were royalty-free outside of France.
Author Ray Bradbury remembers seeing this film when he was a kid and that the ending brought him to tears. Years before his passing, he had the opportunity to see it again. He said that "it still works" and the ending brought him to tears again.
The Comprachicos, a Spanish term meaning child buyers, was coined by Victor Hugo for the novel. According to Hugo, they could change one's physical appearance through various methods such as physical restraints, muzzling their faces to deform them, slitting their eyes, dislocating their joints, and the malformation of their bones.