Originally, the Dali dream sequence was going to be twenty minutes long and feature a shot of Constance covered in ants. Eek. (Source)

The snow falling on John and Constance during the skiing scene isn't snow. It's cornflakes. No wonder John got amnesia; who wants to remember being covered in cornflakes? (Source)

Producer David O. Selznik was a fan of psychoanalysis and had his own therapist consult on the film. (Source)