In the scene when Rhett hands Mammy a glass of whisky, you can see her sniff it before drinking. When it was originally filmed, tea was supposed to have been in the glass, but Clarke Gable (Rhett) substituted real whisky as a joke. The actress playing Mammy downed the glass, not realizing what was in it. The scene had to be redone, with tea, and obviously the actress didn't trust Gable after the first incident. See more...
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There is a very short scene in the second half of the film where Mrs Meade and Dolly Merriweather are sitting at a tea table gossiping about Scarlett's behaviour. There is a teapot in the middle of the table, and Dolly Merriweather is sitting behind it. Yet the teapot is casting a shadow on the wall and Mrs. Merriweather isn't.
After Frank Kennedy's death Scarlett is sitting in her room, "mourning" and drinking. When she hears Rhett's carriage she goes to the window. In this moment you see shadows, either from crew members or equipment, cast through the room, especially visible on the bottle on the table. There is also some funny shift of the backdrop outside the window.