When Alan Jay Lerner met Leslie Caron in London to discuss the film with her, he was surprised to discover that Caron, who was of French birth, had become so immersed in the English culture that she had lost her French accent.
The day after the movie won nine Oscars, MGM telephone operators were instructed to answer all phone calls with "Hello, M-Gigi-M."
When the film was originally completed, Alan Jay Lerner and Frederick Loewe were unsatisfied. Lerner felt it was slow and 20 minutes too long. He proposed changes that would cost Arthur Freed an additional $300,000, which Freed was dead against spending. The songwriting team offered to buy 10% of the film for $300,000, then offered $3 million for the print in order not to release it! Impressed with their conviction, MGM executives agreed to the changes, which included 11 days of re-shoots and put the project $400,000 over budget. However, test screenings of the film changed from favourable (before the change) to affectionate (after the change), and Lerner felt the film was finally complete.
Production was rushed to take advantage of the good weather in Paris, which resulted in the cast having to mouth the songs to piano accompaniment while filming, as the score was not yet recorded.
The Broadway production of the stage play "Gigi" by Anita Loos opened at the Fulton Theater on November 24, 1951, ran for 219 performances and closed on May 31, 1952. The title role was portrayed by then unknown Audrey Hepburn who won the 1952 Theatre World Award for her performance.