Revealing mistake: When the police car crashes through the grating that was dropped down in front of it at the end of the tunnel, the occupants are dummies - they just bounce about in the same upright position whilst the car drives into the river.
Revealing mistake: When McCullough is discussing Prudy's oddities with the matronly lady out front of the mayor's house, it is obvious that the lady is standing on a dirt-covered concrete sidewalk.
Revealing mistake: Although the movie 'Carry On Camping' is supposed to have been set in the summer time, it was actually filmed in November 1968, during a spell of very cold weather. You can actually see the cast's breath in the cold air at some points. The field in which the famous "flying bra" sequence was shot was so muddy, that the mud had to be sprayed green to make it look like grass.
Revealing mistake: Miss Fosdick searches in her filing cabinet, but there are no files visible only the file holders.
Revealing mistake: In the scene where the town is collapsing, there is a shot of Ben in the bathtub falling into the river, if you look closely, you can see the strings that are keeping the tub steady and upright.
Revealing mistake: Near the end of the film, Charlie Brown, Linus and Snoopy all cast shadows from the moon, and then suddenly seconds later all the shadows are fully gone. Also, no shadows were cast from any other object around them when the shadows were shown on the characters.
Revealing mistake: Captain Beckman is in the tower shooting at a small German plane that is attacking the castle. He is told to aim for the engine but when he does and shoots it down its not the engine that smokes, its both the wheels that are smoking from some very obvious smoke tubes attached to the fixed landing gear.