Continuity mistake: At the detective agency, while Bud and Lou are talking to the murderer, the description of the murderer comes over the police radio, and it states "5 feet 11 inches, weighs 165, blue eyes, brown hair, last seen wearing a felt hat and dark borwn overcoat". Then 15 seconds later Bud says out loud, writing on a piece of paper the description "5 feet 10 inches, weight 165, blue eyes, sandy hair".
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: When Hill disturbs Michael Corland at the table, he holds a piece of paper. The paper swaps hands between shots. (00:07:05)
Continuity mistake: In the early scene in the officers' club, the money in the center of the poker table disappears and reappears with the change of angle.