Ann-Margret got to keep whatever she wanted of the wardrobe created for her by Helen Rose as part of her contract to do the movie.
As pre-release publicity MGM sent costume designer Helen Rose to New York City and Chicago with "25 Fabulous Helen Rose Fashion Creations" from the $250,000 wardrobe designed for the film. The first fashion show was presented at the National Press Fashion Show sponsored by The New York Couture Group in January 1966. A week later the famous Pump Room in The Ambassador East Hotel was the scene for the Chicago show, followed by the world premiere of the film at The Chicago Theatre on January 28, 1966. A vial of the Robert Piguet fragrance "Bandit" was handed out to the ladies for the first three days of the movies run in Chicago.
Jacqueline Beer (Denise Marton) costarred with Roger Smith in 77 Sunset Strip (1958). Smith who would eventually marry Ann-Margret (Maggie Scott).
The New York City premiere was held as a fund raiser for the Huntington Hartford Gallery of Modern Art in the Grand Ballroom of the New York Hilton Hotel on Valentine's Day 1966.
Despite its title, and being set mostly in Paris, this film was made entirely on the M-G-M studio backlot in Culver City, California.
M-G-M apparently offered Ann-Margret's role to Doris Day, who was then America's #1 box office draw. Day, who would have given a decidedly different performance, wisely turned it down because she had issues with the script.
The role played by Richard Crenna was originally cast with Bob Crane, who had to turn it down when he landed the title role in a CBS sitcom called Hogan's Heroes. M-G-M was so pleased with Crenna's performance that they signed him to a three picture contract.
The "second male lead" (the role of the flitatious department store heir) was supposed to be played by Richard Chamberlain, who was under contract to M-G-M as the star of the studio's hit TV series Dr. Kildare. When Chamberlain decided he didn't care for the script, Chad Everett (who was also under contract to the studio) stepped into the role.
The banks-of-the-Seine set where Ann-Margret and Louis Jourdan perform "A Paris Lullaby" was also used for the scene where Gene Kelly sings "Our Love is Here to stay" to Leslie Caron in An American in Paris.