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 - chronological order
Directed by: François Truffaut
Starring: Julie Christie, Cyril Cusack, Anton Diffring, Oskar Werner
Visible crew/equipment: Near the end when Montag arrives at the Book Peoples' commune, he is greeted and ushered into a house. There's a shot from just inside the building, looking out a window towards Montag and his host as they approach. As the POV shifts a little, a reflection of the camera becomes plainly visible in the window glass.
Guy Montag: Tell me, this uncle of yours, did he ever tell you not to talk to strangers?
Clarisse: No, he did say once if anyone asked how old I was to say I was 20 and light in the head. They always seem to go together.
Guy Montag: Light in the head?
Clarisse: Mm-hmm, loopy, crazy.
Trivia: The books seen burning at various points in the film include several of Ray Bradbury's novels (Fahrenheit 451 itself is one of these), as well as a French cinema magazine for which director Francois Truffaut once wrote a movie column.