At the recording session for "Here's What I'm Here For", Esther runs across the studio to Norman during the chorus break, whereby a sound man moves his boom mic over to them to pick up their conversation already in progress. However in the playback, their conversation begins at scratch, immediately after the beginning of the chorus break.
After Vicki comes home and she performs in her house for Norman, the doorbell rings and he goes to the door to accept a package for Vicki. His hair is all mussed up when he goes to the door, but after he closes it and the camera goes back to him, there isn't a hair out of place. Then he walks over to where Vicki is and his hair is all mussed up again.
Although the interior of Esther's apartment appears to be situated on a hill with a panoramic view of Hollywood, the address she gives Norman is in the flatlands of Hollywood with, at best, a second story view of nearby buildings.
The opening scenes of cars arriving for the benefit combine actual shots of a Hollywood event with ones filmed for the movie. But in one shot, taken from the perspective of a spotlight crew atop their tower, the footage of the real event is shown on the right side of the screen, while footage shot for the movie is at the left. Not only is the disparity between the two shots obvious, but the split screen is completely mismatched, so that the cars on the right appear to be moving at a sharp angle directly into the cars and building in the shot at left, and it looks as though there are two streets intersecting below.