* CreatorBacklash: He hated ''Metropolis'', regarding it as an OldShame for its childish story motivations, its weak ending, and the fact that [[MisaimedFandom the Nazis]] [[YourApprovalFillsMeWithShame liked it]]. Of his American works, Lang considered ''An American Guerrilla in the Philippines'' his nadir, to the point that he refused to even discuss it with interviewers.
* CreatorCouple: Lang and von Harbou.
* EnforcedMethodActing
** In ''Film/{{M}}'', there is a shot where Peter Lorre is being chased by the mob, and we see a pair of hands reach out and shove Lorre down a flight of stairs. The hands were Lang's own, and the look of betrayal in Lorre's eyes is because ''he was not told'' that the director was about to shove him down a flight of stairs.
** John Ford, watching a scene in "Western Union" where Randolph Scott tries to burn the ropes off his bound wrists: "Those are Randy's wrists, that is real rope, that is a real fire."
* ExecutiveMeddling: Happened a lot with his Hollywood films.
** In ''Fury'', for instance, he wanted the protagonist to be guilty of the crime the lynch mob attacks him for (which would have been suspiciously similar to ''M''), but a sympathetic criminal protagonist wasn't allowable under the Hays Code. Spencer Tracy's climactic speech was originally much longer and angrier in its condemnation of lynching.
** ''Film/{{Metropolis}}'' was famously eviscerated from 153 minutes to less than 90 by Paramount.
** ''Man Hunt'' nearly wasn't released because studio censors labeled it a "hate film," inciting violence against Nazi Germany (at a time America was still neutral in World War II). Fortunately, Daryl Zanuck endorsed Lang's antifascist message and the movie became a hit.
** ''Hangmen Also Die!'' originally ended with the Nazis executing their Czech hostages, including a major character, and [[DownerEnding later survivors visiting their mass grave]]. This ending was finally restored in a 2014 video release.
** ''Cloak and Dagger'' ended with a strong condemnation of nuclear weapons. Possibly under government pressure, this scene was cut and later destroyed by the studio.
* LifeImitatesArt Wernherr von Braun (head of the Nazi rocket program and later NASA) loved "Frau im Mond" and even put a plaque of it on some of his rockets. Some say the tradition of having a countdown prior to launch was also taken from that movie.
* ProductionPosse: Between 1921 and 1933, whatever Fritz Lang did always included Thea von Harbou as the screenwriter and, with only two exceptions (Peter Lorre for ''M'' and Fritz Rasp for ''Woman in the Moon''), had Rudolf Klein-Rogge playing the villain.
** In America, he generally struggled to maintain one since he worked as a studio director and refused to serve under contract to any studio. Likewise his difficult personality as a director in the star-centric Hollywood led to a lot of clashes and movie stars avoided working a second time with Lang if they could help it. His most regular collaborator was Joan Bennett (''Man Hunt, Scarlet Street, The Woman in the Window, Secret Beyond the Door'').
* RealitySubtext: Many of his films with Thea von Harbou cast her ex-husband Rudolf Klein-Rogge (whom she left to marry Fritz) as the villain. A major plot point in ''Metropolis'' is the [[DoesThisRemindYouOfAnything work-obsessed control freak]] Joh Fredersen taking the wife of mad scientist Rotwang (played by Klein-Rogge). The statue of the (dead) wife bears suspicious similarities to Thea von Harbou, so... yeah.
* SequelGap: ''[[Film/DrMabuseTheGambler Dr. Mabuse, der Spieler]]'' received a sequel, ''Film/DasTestamentDesDoktorMabuse'' 11 years later in 1933. It was followed up with ''Film/Die1000AugenDesDrMabuse'', which came out in 1960, 27 years later.
* TechnologyMarchesOn: Out-of-universe example. The first ''Dr. Mabuse'' film, released in 1922, is a SilentMovie. Its sequel, which was made in 1933, is a talkie.