Revealing mistake: To save money during the beach picnic scene, Welles used stock footage from King Kong (1933) for the jungle background. You can quite clearly see pterodactyls flying in the background (confirmed on DVD commentary).
Revealing mistake: When they are inspecting the statues at the end of the movie, somebody touches one of them. It wobbles as if it was made of something else than stone.
Revealing mistake: When the Parrot (or whatever bird it is) cries in a close-up, one can see straight through his eyes onto the sea in the background. Probably a mistake in an optical printer.
Revealing mistake: As the camera moves back (or is it forward?) through the Kane household at the beginning of the movie, you can hear the sound of the camera on the track.
