Continuity mistake: During the archery constest, in one scene Prince John has a ring on his right paw with no jewel, then all of a sudden the jewel appears. a few scenes later he has three rings on that paw, and later he has no rings at all.
Continuity mistake: When Falfa's Chevy flips over, we can see that it has no fuel tank at all in it. However, in the next shot the car now has a visible fuel tank, and it explodes.
Continuity mistake: At one point D'Artagnan reaches the Duke of Buckingham, who is on a hunt. He has just killed a stag and his hands are covered in blood. D'Artagnan rides up and offers him a note from Queen Anne. He wipes his palms with a cloth before he takes the note, but his hands are still covered with blood up to and above the wrists. When he reads the note, he and D'Artagnan take off on foot for his castle where they go into a private room behind the walls. Suddenly it is apparent that his hands are perfectly clean right down to his scrubbed fingernails and, without explanation, the plot-heavy sequence continues.
Continuity mistake: When Barbra Streisand meets Robert Redford on the street at the end of the film, the camera shoots her from behind and her coat collar is standing up. When the angle shifts to the front, her collar is neatly in place.
Continuity mistake: In one scene the actress is wearing a tight fitting sweater which clearly shows that she is wearing a bra. In the next shot she stands up to say she is off to have a shower, whips off her top and - you've guessed it - no bra!
Continuity mistake: In the bedroom scene, Barbara Windor gets her dressing gown caught in the bed spring and has to take it off. When Sid James tries it on, he has no trouble removing it from the bed.
Factual error: When Webster is attempting to open his first safe, on the job, so to speak, he only turns the wheel once. Now, I am not an expert on safes, but I do know that the wheel must be turned back and forth, with the correct numbers, a few times, at least.
Continuity mistake: Vicky is in her office, wearing glasses, until a girl knocks on her door and walks in, and the glasses have vanished.
Factual error: James Caan plays a US Navy Boatswain (Bo'sun) Mate. His rank insignia of BM 1st Class should be worn on the right sleeve, but he has it on the left.