Deliberate mistake: Montag's hair gets intermittently shorter, longer and shorter again (and acquires a "cow lick" that wasn't there before) near the end of the film. (Oskar Werner had clashed with Francois Truffaut and deliberately had his hair cut to spite director.)
Fahrenheit 451 (1966)
1 deliberate mistake
Directed by: François Truffaut
Starring: Julie Christie, Cyril Cusack, Anton Diffring, Oskar Werner
Revealing mistake: Near the beginning, Montag puts on the fireproof clothing to use the flamethrower. It's really footage of him later taking off the same equipment played in reverse.
Guy Montag: To learn how to find, one must first learn how to hide.
Trivia: In keeping with the theme of no books this movie has no text visible anywhere except the opening theatrical logo. Even the credits are not shown on the screen. The only symbols shown in the movie are numbers, such as the 451 medallions on the fire crews and their equipment. Signs can occasionally be seen in the background.