Unlike the character she played, Gloria Swanson had accepted the fact that the movies didn't want her anymore and had moved to New York, where she worked on radio and, later, television. Although she had long before ruled out the possibility of a movie comeback, she was nevertheless highly intrigued when she got the offer to play the lead.
When Gloria Swanson finished Norma's final scene, the mad staircase descent, she burst into tears and the crew applauded. Even though it wasn't the last scene filmed, Billy Wilder threw a party for her as soon as the shot was finished.
When Norma Desmond says to the guard at the "Paramount Studio" gates, "Without me there wouldn't be any 'Paramount Studio'" the words could apply to Gloria Swanson herself, as she was the studio's top star for six years running.
According to Gloria Swanson's daughter, Michelle Amon, her mother stayed in character throughout the entire shoot, even speaking like Norma Desmond when she arrived home in the evening after filming. On the last day of shooting, Swanson drove back to the house she, her mother and daughter shared during production, announcing "there were only three of us in it now, meaning that Norma Desmond had taken her leave."
Montgomery Clift was originally cast as Joe Gillis but quit the production two weeks before filming began because he had already played the kept man of a wealthy older woman in L'héritière (1949). Clift was also wary of appearing in the film because he, like the character of Joe, was having an affair with a wealthy older former actress, Libby Holman. Holman was reportedly worried the film would parody their relationship and told Clift she would commit suicide if he played the role.
Jay Livingston, Ray Evans: The Paramount songwriting duo is seen at the piano at Artie Green's New Year's Eve party. They are singing a parody of their song "Buttons and Bows," from Visage pâle (1948), for which they won an Oscar in 1949, the year this film was made.