- Acting for Two: Brigette Helm plays both Maria and her robotic duplicate.
- Fritz Rasp, who portrays the Thin Man, also plays a cathedral monk in a still-missing scene.
- Bad Export for You: Up until 2003, nearly every version of this movie released in America was based on the heavily edited Channing Pollock version. And then there was the version made in The '80s, an… interesting experiment.
- Box Office Bomb: This movie cost 5.1 million Reichsmarks and made just 75,000 Reichsmarks at the box office; in modern terms this is the equivalent of a $293 million movie earning back $10 million.
- Keep Circulating the Tapes: Every version was different for decades. And the only full version surviving was apparently acquired by a collector before the first cuts were made, then wound up in an archive.
- Missing Episode: Missing a third of the entire movie for many years. Even with the rediscovered version, there are still two missing scenes† , one of which is heavily plot-relevant. To make matters even worse, there have been rumors that there are even more missing scenes that were cut from the film before its German premiere to help shorten the time of the film. It's possible that Lang didn't destroy these scenes and there may be even more unseen footage for this film.
- Lang may not have destroyed those scenes himself, but either the Nazis, von Harbou, or the Allies certainly did. Understandably upset about the Bowdlerization the Americans gave his film, he went to his grave believing that no faithful version of it existed anywhere.
- Reality Subtext: Maybe. Fritz Lang's wife, Thea von Harbou, was originally married to actor Rudolf Klein-Rogge, but she had an affair with Lang and ultimately divorced Rogge. In the movie and in the original book, the woman Hel was married to Rotwang (played by Rogge) but eventually had an affair and married Joh Fredersen. As Harbou wrote the original screenplay and story, it's possible she wrote it as a parallel to her own life situation, so a lot gets made of this coincidence. But on the other hand, Lang and Rogge remained good friends and worked together until Lang left Germany, while Rogge also continued to work with Harbou on several other movies.
- What Could Have Been: Moroder made the rock opera version after outbidding David Bowie, among others, for the rights. God knows what he— scratch that, probably even God doesn't know what Bowie would have done with Metropolis.