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.
The Verdo Justice of the Peace is a very old man, and apparently a longtime local. Yet he pronounces the county name of Los Angeles as "Anjeliss" in the modern fashion. Someone of his generation would be more likely to use the classical form, "Angle-iss."
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.
At the Sneak Preview at the Marcopia Theatre, the first sequence of the Born in a Trunk number, which Garland and Mason are apparently watching from the balcony, is projected in 16:9 ratio, but the rest of the number, as viewed by members of the film audience, in the film itself, is in CinemaScope in the much wider 2.55:1 wide screen ratio.
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 Shrine Auditorium benefit which opens the film takes place in Los Angeles, but a very prominently displayed TV camera displays the call letters WABD which at that time was the DuMont Television Network's New York City station, broadcasting on Channel 5, and would not have a camera crew on hand in Los Angeles to record such an event.
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.
The goof items below may give away important plot points.
Early on, Norman declares his love for Esther by drawing a lipstick graffito on the wall of a theater's very busy backstage. At the end of the movie, which must take place at least a year later, the graffito is still there. Given the daily amount of activity this theater hosts, it strains credibility that nobody ever washed the defiled wall.