Revealing mistake: When Bela Lugosi walks off screen, it's obviously a freeze frame. The swaying tree stops moving and even though he was hit by a car, his shadow is still visible. (00:07:55)
Revealing mistake: When the UFO makes the huge flash that knocks everyone in the cemetery down, one of the police officers kicks a tombstone as he falls and it wobbles back and forth. (00:13:35)
Revealing mistake: When the flying saucers leave the planet, you can see their shadows on the fake planet's surface.
Revealing mistake: The pilots are not sitting on normal seats like in every airplane, but on stools or boxes. (00:04:10)
Revealing mistake: The American pilots fly the plane with no hands. (00:04:10)
Revealing mistake: It's amazing how little equipment is in the plane: a shower curtain, a thermometer, and a cardboard steering wheel. (00:04:35)
Revealing mistake: Jeff Trent, Col. Edwards and Lt. Harper grab some guns and take a walk in the graveyard, and a prop tree almost falls over as Col. Edwards walks by and brushes up against it with his shoulder. (00:57:30)
Revealing mistake: After Tor Johnson drops Paula the police officer comes over to try to wake her. The carpet that's supposed to be the ground crumples under his feet. (01:13:25)
Revealing mistake: Vampira flinches when Inspector Clay fires at her even though she's a zombie. (00:15:05)
Revealing mistake: The woman at the graveyard lets out a scream as she sees the dead bodies. It's obvious that the bodies are dressed up store mannequins. (00:08:40)
Revealing mistake: The "Old man-ghoul" changes appearances drastically throughout the entire movie. In some scenes, it is Bela Lugosi in vampire cape, in others it is the famous "double" who is a head taller than Lugosi, a lot thinner and has a different hairstyle. He covers his face with his cape, but this does not help a lot...
Revealing mistake: When the army is firing at the flying saucers, it's obvious that the sky behind the colonel is made of fabric. (00:18:50)
Revealing mistake: During Criswell's opening and closing narrations it is painfully obvious that he is reading from a cue card. (00:00:30 - 01:16:50)
Revealing mistake: After Clay finally has been killed, you can still see him breathing, and even blinking his eyes.
Revealing mistake: As Tor Johnson holds Paula, the police officer comes up from behind and clobbers him on the head with a wooden stick. He falls to the ground and the entire set including all the trees, shake like they were just in a magnitude 7 earthquake. (01:13:20)
Revealing mistake: Jeff's wife is named Paula and is played Mona McKinnon, but when he is talking to her about having to hush up his UFO sighting, he calls her Mona. (00:12:50)
Revealing mistake: Often during the film, the trees wobbles a lot when somebody touches them, like fake trees. (00:09:50)
Revealing mistake: Why are all of the space ships the same exact size as the planet?
Revealing mistake: When the flying saucers are passing over Hollywood and Washington D.C., there's some shots where you can see their shadows on the fake sky. (00:18:15)
Revealing mistake: Inside the alien spacecraft a battery operated blinking traffic caution signal is used as a prop from another world. (01:04:50)
