Deliberate mistake: After the Tusken Raider has attacked Luke, he raises his stick over his head and shouts. The movement of his clothing is extremely unnatural. During the editing, they put the same footage forward, then backward many times, to add emphasis to his movements, but it looks decidedly odd. (00:29:02)
Deliberate mistake: As the Lotus drives off the pier and enters the water, the exposed underbody is that of a normal car. After it enters the sea, the underbody we see is completely sealed, which it needs to be to allow the car to submerge.
Deliberate mistake: The same group of people wearing the same clothes, including a dancer and bartender, are shown sitting around a bar on two different disco nights. On the first disco night we see them when Tony leaves the bar to go outside after being informed by Joey, what Double J is doing in the car. We see these people again at the start of the second disco night, both nights when we see them, the song "If I Can't Have You" is being played. (00:21:20 - 00:56:30)
Deliberate mistake: Several times during the movie the narrator explains what happens while the book flips its pages. During this, every page is identical to the last one so the animation has simply been copied/reused to save time and money.
Deliberate mistake: After the hotel murder, Brophy makes a series of photographic enlargements to prove Dr. Thorndyke's innocence. However, instead of holding his magnifying glass directly in front of his face as he examines the photos, Brophy angles the magnifying glass far to his right so the movie audience can see the magnifying glass details, but he can't possibly see anything.