Continuity mistake: In some shots, Gort the robot has air vents under the chin. In others there are no vents. (01:19:00)
Visible crew/equipment: When Gort picks up Patricia Neal next to the flying saucer, you can see cables leading down to her body to keep her hoisted. (01:20:15)
Plot hole: Klaatu is shot and his body is lying in a prison cell. Gort leaves the flying saucer and walks all the way to the heavily guarded police station in downtown Washington DC. Gort is 8 feet tall and is a robot plus he uses his noisy death ray to create a hole in the police station to retrieve Klaatu's body and nobody noticed him? On top of that, he walks all the way back to the saucer unseen with a dead body. (01:22:36)
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)
Factual error: In the very beginning of the movie broadcasters around the world are commenting on the mysterious spaceship. To lend a bit of calm and normalcy one broadcaster notes that despite what is happening many people are enjoying the fine spring weather in the Capital, to this end picnics and the wonderful cherry blossoms are plainly depicted. Shortly afterward when Klatu leaves the hospital, he is seen examining the cleaner's tag on the suit he "borrowed". This is where he adopted the name Carpenter. Clearly printed at the top of this tag is the date 7/18 1951, not spring by at least a few months.
Continuity mistake: During the news broadcast, the TV announcer is evenly lit. You can see this in the side view of him, as well as on the TV monitor that's next to him. Then, just after he says "there is no reasonable cause for alarm," the microphone in front of him is suddenly casting a big shadow on him.
Revealing mistake: As Klaatu enters the control room of the spacecraft for the first time, we see the right side panel revolve so he can enter. Once inside, it is the other side of the panel which closes.
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: Patricia Neal is in flats as she runs across the field to give Gort the message. When Gort picks her up, she's in heels.
Character mistake: At the beginning of the film, the British radar-man says it's moving at 4,000 mph. Then says it must be a Buzzbomb. As a British radar man, he'd know that the Buzzbomb, or V1 rocket, only flew at 360 mph - 75% were shot down by the RAF.
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.
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.
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.
Other mistake: Lock Martin is not wearing his Gort glove on his right hand in the first frame of him carrying Patrica Neal.
Answer: They said, how they handle their earth problems is no concern to them, it's only if they bring it to outer space and other worlds, they would take drastic measures to ensure that did not happen.