The production went through four directors. Richard Thorpe shot the first footage but was removed by producer Mervyn LeRoy after about two weeks; accounts suggest that his approach to the material was not working. George Cukor replaced him briefly and was responsible for some of the creative decisions that shaped the final film, including removing an exaggerated comedic makeup look and returning Garland to a more natural appearance. Cukor left to manage a production crisis on Gone with the Wind, and Victor Fleming took over the bulk of the shoot. Fleming was himself pulled away before completion to take over directorial duties on Gone with the Wind from Cukor, and King Vidor directed the final days of filming, including the Kansas sequences shot in black and white.
For Garland, the most consequential aspect of the production was not the director changes — though four directors in a single production created obvious challenges for continuity and creative direction — but the physical demands of the schedule combined with the pharmaceutical management that accompanied it. Production of a Technicolor fantasy film in 1938 meant intensive studio lighting, elaborate costume and makeup preparation, lengthy rehearsals for musical numbers, and the technical demands of new color film technology that required multiple takes for lighting and exposure reasons. The working days were long. The set conditions were physically taxing.
The pills that had already been introduced into Garland’s routine continued during production. Amphetamines during the day to maintain energy and appetite suppression; barbiturates at night to counteract the stimulants and produce sleep. This pharmaceutical cycle — stimulant and depressant, wake and sleep, on and off — was not unique to Garland among MGM performers. She later said that the pattern was widespread, that pills were a routine part of the production environment, and that the gradual acclimation to pharmaceutical management of her own functioning had begun before she was old enough to fully understand what was being done to her.