Plot hole: In the scene at Arlington cemetery, Klaatu asks Bobby if it costs money to go to the movies. Bobby states he has $2 his mother gave him, which Klaatu trades for two diamonds. That being said, how in the world did they get from NW DC to Arlington in Virginia, and then on to the Lincoln Memorial at the Mall in DC? Much too far to walk, and Bobby made no mention of money he had before to take a bus or cab. (00:30:30)
Continuity mistake: In the newspaper headlined 'Step up Hunt for Spaceman' the photo on the right shows Klatu and Gort on the hull of the ship. This shot is a still from the end of the film. (01:07:36)
Revealing mistake: When the spaceship is going to take-off, every scientists are trying to escape, but there's a man wearing a light colored suit and hat who seems more interested in pushing the chairs everywhere than escaping. He even pushes a chair in another row. The director obviously told the actors to push some chairs to create more excitement in the scene, but he seems to take that too seriously. (01:31:05)
Revealing mistake: In a few scenes the stitches holding together the front and back halves of Gort's "metal" body can be seen.
Continuity mistake: Just after Klaatu gets shot, Gort is seen melting the clear glass/plastic/cement material he was encapsulated in. When Patricia Neal begins to approach the space ship, the camera shows Gort still melting the material with it almost down to his ankles by this time. The next shot shows Ms. Neal looking at him, but when the camera goes back to Gort, the cement he was encased in is suddenly back up around his waist. How did it get back up when moments before it was down around his ankles?
Continuity mistake: When the power goes out there is a scene where it shows all the cars not being able to work, although in the background there is a movie marquee with the lights on.
Continuity mistake: At the end when the spaceship is about to take off the people rush away from their chairs in fear of the launch. After the ship launches there are no chairs anywhere on the field, just the people.
Revealing mistake: After Gort takes out the guards and Carpenter passes by him, Gort turns around to follow, and the zipper for the costume is visible.
Other mistake: As the UFO approaches and flies over the park, the camera pans to the right with the UFO in the upper left corner of the shot, tracking it. As it does, the UFO passes over the heads of two women, who are gazing at a spot behind where the UFO is when they should be turning their heads to the right, watching the descent.
Factual error: When Bobby and Klaatu are leaving the Lincoln Memorial, Klaatu asks Bobby where Professor Barnhardt lives. Bobby responds, "near where my Mom works, at the Department of Commerce." There is no residential neighborhood as depicted as the location of Barnhardt's house anywhere near the Department of Commerce. (00:32:05)
Continuity mistake: After the power comes back on, a newspaper front page has Klaatu pictured with the president standing just outside the entrance to the saucer's dome, and Gort standing about five feet in front of Klaatu in the same place. But early in the film, Klaatu was on the ground with the president, and Gort never preceded Klaatu coming out of the saucer.