A very troubled production, this movie went way over budget and was a box-office flop when released. Writer, producer, and director Blake Edwards used the experience of making this movie as the inspiration for the script to S.O.B. (1981).
Because of the students' rebellion and strike that paralyzed Paris, France in May 1968, the movie producers moved to Brussels, Belgium to film the major scenes (June to July 1968). For example, it was possible to use the Superior Court building and transform the ground floor into a Paris railroad station with fake trains and a waiting room and all of the other accessories.
The manager in charge of hiring the extras to shoot a scene in the Palais De Justice (Superior court) in Brussels in lieu of the Paris railroad station gave away a fixed number of tickets and requested the ticket holders to come back for work around midnight. Some of the left-wing activists (Socialists) bought a roll of the identical tickets and passed them out to mostly students from the nearby University (Université Libre de Bruxelles) and asked them to show up before midnight. Because they were there early, they were able to get into the courthouse with no problem. They were given costumes almost right away, and when the real extras showed up, the guys in charge were puzzled that there were so many in line considering that the huge hall was already half full. It took them a few minutes before they figured that they had been fooled and outsmarted by the local activists. They were forced to turn away those who had the phony tickets and accept only few of the legitimate hired extras.
One of the first movies to use "video assist" - the process of using a monitor to show what the cameras were shooting and watching the footage afterwards.
The opening number, "Whistling Away The Dark", was performed by Dame Julie Andrews in a single, uninterrupted take.