- Although the film is in black and white, two frames where the gun shot goes off while pointed at the camera are tinted red.
- about 40 minutes in, coming out of the elevator at the Empire Hotel carrying a violin case and smoking a cigarette.
- One of the first Hollywood films to deal with psychoanalysis.
- The dream sequence was designed by Salvador Dali, and was originally supposed to run for 20 minutes. It included a scene with Dr. Peterson covered in ants. Only part of it was filmed, and even less of it ended up in the release version.
- The shot where the audience sees the killer's view down a gun barrel pointing at Peterson was filmed using a giant hand holding a giant gun to get the perspective correct.
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