The 1960 stereo issue of this movie's soundtrack album (Imperial LP 12068W) is considered one of the rarest in the history of vinyl collecting.
Although Walter Bernstein was most anxious to re-establish himself in movies after several years on the blacklist, he asked that his name be removed from the credits of this movie as he disliked it so much. He also insisted to interviewers that a great deal of it was actually directed by the uncredited Vittorio De Sica, who insisted on being paid in cash at the end of each working day.
After Walter Bernstein had his name removed from the credits, the only scriptwriter mentioned for this movie was Sidney Howard, credited with "adaptation". Howard had done an English-language version of Molnar's play for Broadway in the 1920s. By the time this movie came along, he had been dead for over twenty years.
This was the first film directed by Michael Curtiz outside a Hollywood studio since 1926 and was somewhat overwhelmed by Vienna. Sophia Loren found his heavy Hungarian accent and mangled English hard to understand, such as the instruction "Please stand a little closer apart".
Charlie Foster's (John Gavin's) question about the Crown Prince who shot himself and "that girl" is a reference to the Mayerling incident where Crown Prince Rudolf of Austria murdered his lover, Baroness Vetsera, and then took his own life. The incident has been depicted in several movies, including Mayerling (1968) and Mayerling (1936).