Fritz Lang wanted 4,000 bald extras for the Tower of Babel sequence, but Erich Pommer could only find 1,000 willing to shave their heads. Since the scene was shot in the spring, these extras got to swelter under the hot sun shooting the exteriors as they hauled prop rocks and real tree trunks across the landscape. Some got sunburns on their scalps from the lengthy shoot. After shooting, Lang ordered the shot run through the optical multiplier to make the 1,000 extras seem like the 4,000 he had originally wanted.
Much to Fritz Lang's dismay, Adolf Hitler and Joseph Goebbels were big fans of the film. Goebbels met with Lang and told him that he could be made an honorary Aryan despite his Jewish background. Goebbels told him "Mr. Lang, we decide who is Jewish and who is not." Lang left for Paris that very night.
Unemployment and inflation were so bad in Germany at the time that the producers had no trouble finding 500 children to film the flooding sequences.
The nightmare in which workers are fed to Moloch was filmed in the middle of winter. Despite the lights and several heaters, the studio was extremely cold, a special hardship on the extras, most of them unemployed men, who had to walk naked into the mouth of the god. Fritz Lang took so many days filming the sequence his assistants feared the extras would revolt. Finally, Erich Pommer came to the set and informed the director that he had more than enough footage already and needed to stop.
For decades, all that survived of Metrópolis (1927) were an incomplete original negative and copies of shortened, re-edited foreign release prints; over a quarter of the film was believed lost. However, in July 2008, Germany's 'ZEITmagazin' reported the discovery of a 16 mm dupe negative copy of the film at the Buenos Aires Museo del Cine Pablo Ducrós Hicken by film historian and collector Fernando Martín Peña. Up until then, all that was known was that a original, full-length 35mm export print had been sent to Argentina in 1928. The last officially documented screening of this version had occurred in the 1950s and was considered lost. However, since 35 mm film was more hazardous to keep in those days (The nitrate inside the negative could sometimes ignite.), preservers would often make a 16mm negative copy of the original film that was easier to store. What prompted the discovery was that Martín Peña remembered stories from Argentinian movie operators claiming to have screened a version of Metropolis of over 2 hours long in the 1980s. (The only known versions at the time were all considerably shorter.) This version had probably been part of a private collection that was later donated to the museum. After finally getting permission to search the museum archives, Martín Peña found the surviving 16 mm copy. Examining the reels in Buenos Aires, cinema experts realized that the copy had a relatively poor picture quality, mainly because it had also copied all the damage from the original 35 mm film that had been worn from years of use. The copying process from 35 to 16 mm film also meant that some parts of the frame had been lost. Nevertheless, the reels contained almost all of the previously missing sequences (around 25 minutes-worth of footage, predominantly those involving the Thin Man, who spies on Freder, and worker 11811 heading to and from Yoshiwara). Additionally, in October 2008 it was announced that another (hopefully) early copy in the obsolete 9.5 mm format had been held in the University of Chile's film library, intentionally mislabeled to avoid destruction during 1973's military coup. It is as yet unknown if this holds any further viewable footage. The missing scenes from the 2008 16 mm copy were cleaned up as best as possible, reframed into the 4:3 aspect ratio to match the original footage, and re-edited into the film based on the original screenplay. After almost 80 years, the film is now practically complete, barring sections such as Freder listening to a priest giving a sermon on the coming apocalypse and Joh Fredersen's fight with Rotwang.