Continuity mistake: When the quake starts, Joyce Hendron runs to the arms of David Randall for protection. Ten seconds later, she again runs again to his arms. (00:41:55)
Continuity mistake: Klaatu introduces himself to the Professor for the first time by relaying some details of his stay at the hospital to verify who he is. Klaatu tells the Professor he was staying in room 309, but the early scenes at the hospital show him in room 306. (00:41:48)
Continuity mistake: In the scene where Guy enters Bruno's house to kill his father, Guy takes out a flashlight to look at Bruno's map. In one shot, you can only see the map, and the light is very small and circular, but in a wider shot of Guy's upper torso, the light covers most all of the map.