Filming was completed a short time before D-Day and the director, having planned to distribute the film after the liberation of France, had three copies printed and concealed in three different places: a cellar of the Banque de France, a strongbox of Pathé and a Provence country house.
This involved building the largest studio set in the then history of French cinema - the quarter mile of street frontage, reproduced in scrupulous detail, representing the Boulevard du Crime, the theater district of Paris in the 1830s and 40s. This would have been a daunting prospect at the best of times but in Vichy France, when all artisans, transport, materials, costumes and film stock were all in short supply, it was a miraculous achievement.
The film's title refers to the people who sat in the upper balcony of the theatre. This is where the lower classes sat, as the seats were significantly cheaper that the ones below (as noted in the film itself). It is the French equivalent of the term used in English theatres, "the gods."
A large number of members of the French Resistance worked on this film's crew, as Nazi power was at its peak in France and these fighters needed concealing.
Production designer Alexandre Trauner and composer Joseph Kosma - both Jews - had to work in hiding and submit their ideas via intermediaries since filming occurred when France was still occupied by Nazi Germany. But, when the film was finally released in the spring of 1945, France had been liberated, and both men's name were listed on the credits.