Melanie Wilkes is described as a plain girl in the book and is liked because she is kind and sweet to everyone. Olivia de Havilland is far too pretty to be believable as a plain girl, but she is easily believable as the kind Ingenue that everyone loves.
Scarlett also isn't remotely beautiful in the book. She's decent looking but her appeal comes from her personality and lack of attainability. Vivien Leigh might be too pretty but she captures Scarlett's personality to the T. The original author gave Leigh her stamp of approval.
Adored by the Network: AMC loves to air this around Thanksgiving, even though it has nothing to do with the holiday and isn't really the kind of movie that appeals to all ages.
It's been noted several times this is Ted Turner's favorite movie, and not only did he end up owning it (thanks to acquiring MGM for 74 days in 1986, then selling it back, but kept the MGM library up to that point), it was the first program shown on both TNT and TCM. For years there was a theater at the CNN Center that offered showings of this movie (it was replaced by areas for CNN's websites in the late 90s).
Creator Backlash: Very few of the cast members actually liked the characters they were portraying. Butterfly McQueen regretted playing such an Ethnic Scrappy, Leslie Howard felt he was too old for Ashley and hated the costumes, and Rand Brooks disliked playing Scarlett's first husband as he was a rough outdoorsman and disliked such a wimpy character.
Dawson Casting: Leslie Howard was 47, and felt he was far to old to play the twenty-something Ashley Wilkes. Justified because this film covers over ten years, and so he had to play the older Ashley as well. Also, Vivien Leigh was 26 years old when cast as the 16 year old Scarlett. Like the Howard example, this was justified as she continued to play Scarlett as the character aged.
When Melanie goes into labour, Olivia de Havilland had someone pinching her toes off camera to make her feel pain.
While directing the scene where Prissy says, "Oh Miss Scarlett! I don't know nuthin' 'bout birthin' babies," George Cukor told Vivien Leigh to actually slap Butterfly McQueen and to make it as realistic as possible, and directed McQueen to scream. After many takes McQueen broke down in tears, complaining that Leigh was hitting her too hard. In a later interview, McQueen said that she "bargained" with the others, stating that if Leigh hit her, she would NOT scream, but if Leigh's hand only passed close to her face with the illusion of hitting her, she would scream as loudly as she could. McQueen also giggled and said that she thought "Prissy should have been slapped often, because she was horrid!"
David O. Selznick tried to talk Louis B. Meyer out of making the film, saying, "Forget it, Louis. No Civil War picture ever made a nickel". He wound up eating those words...
Gary Cooper turned down Rhett Butler because he thought the film would flop. Oops.
Jossed: Vivien Leigh and Clark Gable repeatedly denied the newspaper rumours that they weren't getting along on the set of Gone with the Wind. They found the rumours so funny that they would frequently greet each other by saying "How are you not getting on today?"
Clark Gable only agreed to do the film because the money would allow him to divorce his current wife and marry Carole Lombard.
Leslie Howard didn't even bother reading the book, and only did the film because Selznick promised him that he could fulfill Howard's dream of becoming a producer. His contract stipulated that he could produce, direct, and star in any movie of his choice. That film was Intermezzo, a remake of the Swedish film of the same name, which ended up being a Breakout Role for co-star Ingrid Bergman.
Non-Singing Voice: Variation. The retching noises Scarlett makes as she delivers her famous "with God as my witness" line were dubbed by Olivia de Havilland. Rumour is that Vivien Leigh either couldn't do it the way the director wished, or refused because it wasn't ladylike.
Playing Gertrude: Barbara O'Neil, who played Scarlett's mother, was only three years older than Vivien Leigh. She was twenty-eight to Leigh's twenty-five. Granted the mother only appears in the part of the story where Scarlett is sixteen-seventeen (and Leigh plays her across several years) and young mothers were quite common in the South. But still very noticeable.
Prop Recycling: The MGM lot had many old sets that were due for demolition. Instead, they set fire to them to film the burning of Atlanta. The gates from King Kong is the burning wall that almost collapses on Rhett and Scarlett's speeding wagon.
The Red Stapler: Uncertain, and definitely downplayed. Scarlett appeared in the top 1000 female names in 1940, a year after the movie came out, and lasted four years. The name reappeared in 1962 and 1963. It reappeared in 1992, then gained in popularity in the 2000s, reaching 30th in 2014.
Throw It In!: When Rhett pours Mammy a drink after the birth of Bonnie, for a joke during a take, Clark Gable actually poured alcohol instead of the usual tea into the decanter without Hattie McDaniel knowing it until she took a swig.
Vivien Leigh wasn't happy with Victor Fleming's brusque style after the careful nurturing she had enjoyed with George Cukor. When she asked him for direction in one scene, he told her "Ham it up". On another occasion when she asked for his constructive advice, he told her to "take the script and stick it up her royal British ass". After Cukor's departure, Leigh had to fight hard to keep the movie's Scarlett true to her view. Fleming's interpretation of her was that she was an out-and-out bitch as in the novel and that he had no desire to create any sympathy or insight for her.
Clark Gable supposedly had George Cukor fired as director.
Gary Cooper was the first choice for Rhett Butler. He turned it down, expecting the movie would flop. Margaret Mitchell's first choice was Basil Rathbone. She also jokingly suggested Groucho Marx, as she didn't seriously think that her book would be adapted into a film. Fredric March was also considered.
Katharine Hepburn was a leading contender for Scarlett, but she refused to do a screen-test. Legend has it that David O. Selznick turned her down, saying, "I just can't picture Clark Gable chasing you for seven years".
Bette Davis turned down the role of Scarlett O'Hara, thinking that her co-star would be Errol Flynn, with whom she refused to work.
Alfred Hitchcock wrote a treatment for the scene where the women wait for the men on the raid from Shantytown at the request of the director. His treatment included precise shots, showing Rhett and Ashley dodging the Union soldiers - and a meaningful exchange of glances between Melanie and Rhett. None of this was used.
Judy Garland was heavily in the running to play Scarlett's sister Careen but she was too busy filming The Wizard of Oz - so Ann Rutherford was cast instead. Billie Burke, who played Glinda, auditioned for Aunt Pittypat but was turned down for being too young.
Early drafts of the script kept in Scarlett's son Wade but he was cut from the story before filming began. He still appears in a book of paper dolls about the characters that was printed before he was cut.
The final scene was to be of Scarlett clad in a green dress, approaching Tara. This was filmed (stills can be found on YouTube), but cut.
Of all the actresses considered for the role, Louise Platt, Tallulah Bankhead, Linda Watkins, Adele Longmire, Haila Stoddard, Susan Hayward (at the time using the name Edythe Marriner), Dorothy Mathews, Brenda Marshall, Paulette Goddard, Anita Louise, Margaret Tallichet, Frances Dee, Nancy Coleman, Marcella Martin, Lana Turner, Diana Barrymore, Jean Arthur, Joan Bennett and Vivien Leigh were given actual screen tests for the role of Scarlett O'Hara.
Hattie McDaniel was cast as Mammy after Louise Beavers, Etta McDaniel, Ruby Dandridge, and Hattie Noel were briefly considered.
Although Olivia de Havilland was always front-runner to play Melanie, Janet Gaynor, Fay Wray, Jane Wyman, Anne Shirley, Priscilla Lane, Marsha Hunt, Gloria Stuart and Andrea Leeds were also considered. Reportedly when Joan Fontaine was considered for the role, she rejected it but suggested her sister de Havilland for the part. Shirley, Hunt and Leeds were the only ones who underwent a screen test for the part.