Revealing mistake: During the car chase scene, if you watch the speedometer on the car, it never rises above zero. That and the obviously poor image quality of the "road" in front of them shows that they were using projected film in front of the car.
Revealing mistake: When the farmer is going to shoot the sign the bank put up, you can very well see the mark where the hole is going to appear.
Revealing mistake: In the scene where King Arthur expounds on the joy of his kingdom, he has a Band-Aid on the back of his neck. (00:21:00)
Revealing mistake: The flashlight that the drillman used when the lights went out around the spaceship didn't match the light from the spot used by the film crew.
Revealing mistake: In the beginning when Mrs. Meers goes into the elevator, you can see that the elevator floor is a continuation of the room floor, just with a strip across it.
Revealing mistake: When the tank/truck driven by Marvin is crossing the stone bridge at the end, they are met by a small German gun vehicle, which they run off of the bridge. The camera angle changes to below the bridge and you see the German vehicle fall from the side of the bridge into the water below. If you look at the bridge material that shatters you can see pieces of wood and hollow areas where obviously it's not real stone. (02:25:00 - 02:30:00)
Revealing mistake: When Spencer Tracey backs his car into the hotrod at the ice cream stand, you can see the hotrod already has a sizable dent before the car makes contact, probably a result of a previous take.
Revealing mistake: It is obvious that the night scenes were filmed in broad daylight, since clear shadows are still cast on any available surface.
Revealing mistake: At the end when the class are having their dance, the band manage to play without any amps, speakers or mikes. We even hear keyboards, despite no-one playing any.
Revealing mistake: The day after their first date Benjamin drives through the pouring rain to pick up Elaine. If you look closely out the side windows of the car you can see that it's produced by a rain machine, it's actually a beautiful day with the sun shining. (01:07:40)
Revealing mistake: During the pie fight sequence Brenda is obviously wearing a wig as her hair suddenly becomes twice as thick as it was before.
Revealing mistake: When Old Timer strikes it rich and digs his gold mine, the rock he is digging and mining is obviously not gold, just ordinary rock.
Revealing mistake: The Union Flag pinned to the back of the taxi driver's jacket is upside down. Since he is part of the government (he's undercover for the Foreign Office) he shouldn't make such an terrible mistake. (01:20:40)
Revealing mistake: In the scenes inside the space capsule, as Roy goes through the sequence, the wires holding him up in the floating sequences, and the crackers when trying to eat, are visible.
Revealing mistake: When the sky bike is flying during the competition it is obviously suspended from a crane as you can see the wires.
Revealing mistake: Inspector Emil arrives at the morgue; pay attention to the body, just before he asks "You are...?" to Armstrong, the sheet covering the cadaver rises and fall as the departed takes a few deep breaths. (00:32:00)
Revealing mistake: When Dr Dolittle is talking to the parrot and it raises its left leg, you can see a piece of string running past Dolittle's head used to raise its leg.
Revealing mistake: Despite the best efforts, you can tell the fabled white rhino is just a prop on wheels.
Revealing mistake: In the bull ring scene, in the close up shots it's Raquel Welch, in the pulled back shots it's obviously a stuntman in drag with her voice dubbed in.
Revealing mistake: When Dr Kilmore crashes through the window of the bathroom at the nurse's home, it is not Jim Dale but a stunt double.