"My Fair Lady" is the only Alan Jay Lerner and Frederick Loewe stage musical to have been filmed totally complete, with no omission of any songs from the stage version (or dialogue, for that matter). There are even some added lyrics to the song "You Did It", in which Higgins goes more into detail about the speech "expert" Zoltan Karpathy's evaluation of Eliza at the ball, that were not in the stage version. My Fair Lady, West Side Story, and South Pacific may be the most complete film adaptations of Broadway musicals ever made.

Audrey Hepburn announced the assassination of Pres. John F. Kennedy to the devastated cast and crew immediately after filming the number "Wouldn't It Be Loverly?" on the Covent Garden set on 22 November 1963.

Audrey Hepburn herself revealed years later that had she turned down the role of Eliza, the next actress to be offered it would not have been Julie Andrews but Elizabeth Taylor, who wanted it desperately.

Audrey Hepburn later admitted she would never have accepted the role of Eliza Dolittle if she had known that producer Jack L. Warner intended to have nearly all of her singing dubbed. After making "My Fair Lady", Audrey Hepburn resolved not to appear in another film musical unless she could do the singing on her own.

Connie Stevens, then a Warners contract player, campaigned for the role of Eliza Doolittle.

George Cukor and Cecil Beaton - who were good friends beforehand - had a big falling out during the production. This is generally thought to be down to Beaton taking too much time photographing Audrey Hepburn when Cukor wanted her for rehearsals or filming. These were in fact the only times that Beaton - credited as the film's production designer - ever showed up on set.

Jeremy Brett, who celebrated his 30th birthday during filming, was very surprised to learn that all of his singing was to be dubbed by a 43-year-old American named Bill Shirley, especially since his own singing voice at that time was remarkably good.

Robert Coote was nominated for the 1962 Tony Award (New York City) for Supporting or Features Actor in a Musical for "My Fair Lady" for his role as Colonel Pickering and recreated that role in the 1976 Broadway revival.

Rex Harrison wanted Julie Andrews for the role of Eliza, since they had played together in the Broadway version. He was concerned that Audrey Hepburn, whose mother was a Dutch baroness, would not be able to play a "guttersnipe" effectively. However, after finishing the film, Harrison had the highest regard for Hepburn's performance, and later referred to her as his favorite leading lady of them all. (It should also be mentioned that Harrison was appalled by Andrews during initial rehearsals for the original Broadway production of "My Fair Lady". Andrews was having a lot of trouble with the characterisation of Eliza Doolittle, and the Cockney accent. So much so, that Harrison was once quoted as saying: 'If that girl is here on Monday giving the same goddamn performance, I am out of this show!')

Rex Harrison was very disappointed when Audrey Hepburn was cast as Eliza, since he felt she was badly miscast and he had hoped to work with Julie Andrews. He told an interviewer, "Eliza Doolittle is supposed to be ill at ease in European ballrooms. Bloody Audrey has never spent a day in her life out of European ballrooms." Nevertheless, Harrison was once later asked to identify his favorite leading lady. Without hesitation, he replied, "Audrey Hepburn in My Fair Lady."

Rex Harrison's microphone (hidden in his neckties) would occasionally pick up police broadcasts from passing police cars.

Cary Grant told Jack L. Warner that not only would he not play Henry Higgins, but if Rex Harrison was not cast in the role, he wouldn't even go see the picture.

Walt Disney offered to delay filming on Mary Poppins until the summer of 1964 if Julie Andrews was cast as Eliza.

Julie Andrews got her revenge on Jack L. Warner three years later when she wasn't cast as Guinevere in the film version of Camelot, a part which she had made her own on Broadway. Her Great White Way co-stars Richard Burton and Robert Goulet were also not cast in the film, which went on to flop so badly for Warner Brothers that the company ousted Jack L. Warner as their president.

Julie Andrews was the first choice for the role of Eliza Doolittle, but Warner Brothers, which had paid $5 million for the rights to the Alan Jay Lerner and Frederick Loewe musical, didn't want to risk a stage actress in the central role of a $17-million film, despite lobbying from Lerner himself. However, this reason has been strongly doubted by those who believe audiences would have flocked to see the film regardless of who played the leading role. It is also reported that Jack L. Warner didn't think Andrews would be photogenic enough. He invited her to do a screen test, but she refused, so he forgot about her altogether.

Stanley Holloway originated the role of Alfie Dolittle on Broadway, but it was thought that a better known actor would be more suited for the film version.

Stanley Holloway was nominated for the 1957 Tony Award (New York City) for Supporting or Features Actor in a Musical for "My Fair Lady" for the role of Alfred P. Doolittle and recreated the role in the movie version.

Alan Jay Lerner was very annoyed by Jack L. Warner's decision to have the entire movie filmed on sound stages in Hollywood, even for outdoor scenes.

George Bernard Shaw adamantly opposed any notion that Higgins and Eliza had fallen in love and would marry at the end of the play, as he felt it would betray the character of Eliza who, as in the myth of Pygmalion and Galatea, would "come to life" and emancipate herself from the male domination of Higgins and her father. He even went so far as to include a lengthy essay to be published with copies of the script explaining precisely why Higgins and Eliza would never marry, and what "actually happened" after the curtain fell: Eliza married Freddy and opened a flower shop with funds from Colonel Pickering. Moreover, as Shaw biographers have noted, Higgins is meant to be an analogue of the playwright himself, thus suggesting Higgins was actually a homosexual. Under heavy pressure from producers, for the 1938 film version of "Pygmalion", Shaw wrote a compromise ending, in which Eliza and Higgins reconcile, but Eliza still leaves to marry Freddy. This was later changed without Shaw's knowledge or permission to a conclusion in which Eliza returns to Higgins and supposedly marries him; it is that ending that is used in "My Fair Lady."

Joshua Logan wrote in his autobiography that he was offered the chance to direct the film, but the offer was withdrawn when he suggested that some scenes be shot on location in London.