In the opening scene, Theodore Pierce is shown on a ledge with his back up against the building. The ledge is reasonably wide, and his feet are clearly at least a couple of feet from the edge. When the camera goes in for a closeup, however, his feet are right at the edge, implying a much narrower ledge.
In addition to the above, in the long shot, he is standing in front of the window . . . the seagull lands . . . and cut to the closeup, he is now on the ledge between two windows. There was not enough "real time" for him to move sideways on the ledge.
In the opening scene, Teddy Pierce is standing on a ledge in front of an open window. However, in the very next shot (a close-up), the window is closed.
When Teddy is on the ledge, the slippers he 'borrowed' from Charlotte's husband are several sizes too big, but as he is falling down they are suddenly a perfect fit.
When Charlotte says 'Come and Get It' to Teddy she has a big smile on her face, but when it cuts to a wide shot of them both her expression is suddenly calm.
At the end of the movie while Charlotte and Teddy are undressing in her living room, there is a pair of black ladies pumps in the background of the bedroom that disappear when the characters walk into the bedroom.
The calendar on Teddy's office wall is for October 1984 showing the first day of the month as a Friday, but 10/1/84 was a Monday.
Teddy is shown boarding an 8:30 p.m. flight from San Francisco to Los Angeles in October while it is still daylight outside. Sunset in San Francisco that time of year is around 6:30 p.m., so it should have been pitch dark.
At the birthday party scene, Charles Grodin can be seen in the mirror waiting for his cue line to enter when Teddy is trying to explain who Charlotte is to his relatives.
When Charlotte gets into the waterbed, there is no sound of the water when she puts her body on the bed.
When Gene Wilder's character is backing into his parking space after standing up Gilda Radner's character, he appears to be looking into a rear view mirror in the car but when Gilda's character approaches to damage his car, there is no rear view mirror in the car. There was a rear view mirror in the previous scene involving the car, as well as the next scene involving the car. Also, later in the film the rear view mirror disappears once more when Teddy is driving with Buddy.
When Gene Wilder jumps from the ledge, he is seen bracing himself for landing, just before he exits the camera frame, indicating a much shorter drop than is portrayed.
When Ted is beckoned to Charlotte's car, it is raining, but when he passes in front of her car, you see blue skies behind him.
Flustered after being invited on a date by an unwitting Teddy, Ms. Milner gets up and runs out of the office. In the process, she bumps into the water-cooler, knocking off the bottle. As it hits the floor, we hear the sound of glass breaking. However, the bottle remains intact, and it's made of plastic, meaning it's impossible for it to have made that sound.
When Teddy enters a room with his arms full of books, the lady speaking to the group of people is heard saying "extra helpings", but her mouth appears to say something different to this.
When Teddy is chatting to Charlotte whilst horse riding, he tries to explain 'the other night' (referring to the date he thought he had with her to which he did not turn up) to which she is bemused. However, Teddy had previously realized with whom he had actually been making arrangements with all along when he turned up for the second 'date' and found Ms. Milner there rather than Charlotte- so bringing this up to Charlotte makes no sense.