Revealing mistake: When the Interceptor team flies in their cargo plane to Mexico to investigate the UFO crash, several shots filmed from the front show the six of them all in the cockpit (not in the body of the plane.) They're seated as they might be in a car, three across, front and back. The window of the cockpit looks remarkably similar to a station wagon windshield, down to the large rectangular front windshield, and even the rear view mirror is in place.
Revealing mistake: When the Japanese tanks are firing upon Godzilla, one of the pyro effects catches the Godzilla suit on fire (at the arm). One can see the stunt man begin to frantically shake his arm upon this realization before the editing cuts to another shot.