Writer Hans Janowitz wrote the female lead character for his girlfriend Gilda Langer, an actress at the "Residenz-Theater" in Berlin but it is Lil Dagover that finally got the role.
Weeks before the initial release of the film, posters with the tag-line "Du mußt Caligari werden!" ("You have to become Caligari!") were put up in Berlin without the slightest hint that they were promotion for the upcoming movie.
Writer Hans Janowitz claims to have gotten the idea for the film when he was at a carnival one day. He saw a strange man lurking in the shadows. The next day, he heard that a girl was brutally murdered there. He went to the funeral, and saw the same strange man lurking around. He had no proof that the strange man was the murderer, but he fleshed the whole idea out into his film.
In the May 12, 1921 edition of the Chicago Daily News, Carl Sandburg wrote of the film: "It is a healthy thing for Hollywood, Culver City, Universal City, and all other places where movie film is being produced, that this photoplay has come along at this time. It is sure to have healthy hunches and show new possibilities in style and method to our American Producers."
Made before "horror" was a designated genre, this is sometimes cited as the first true horror film (although films with elements of the macabre were certainly made earlier).
The trivia items below may give away important plot points.
Director Robert Wiene added the opening and closing scenes to Hans Janowitz and Carl Mayer original script in order to make the film more commercially viable. Fritz Lang claims to have suggested the introductory scene when first presented with the script.