Other mistake: The exhaust of the space ship is so strong that it knocks down Jeff and Paula to the ground, but their hair doesn't get changed at all.
Deliberate mistake: They keep using the same footage of Bela Lugosi walking in the cemetery, even the cars driving by out on the road are the same. (00:53:00)
Continuity mistake: When the flying saucers are spotted over Wash DC, the scene shows a rotating radar antenna. First it's rotating counter-clockwise, then in a subsequent scene it's rotating clockwise. (00:17:45)
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)
Deliberate mistake: At Tor Johnson's funeral how on earth could they not see Vampira standing right next to them? (00:17:00)
Continuity mistake: When the flying saucers are flying over Hollywood, it's nighttime in some scenes and daylight in others. (00:17:45)
Audio problem: The stewardess comes into the cockpit and the co-pilot says, "Well, I know a friend that will help us". If you look closely, he was going to say more but it was edited out. (00:28:50)
Visible crew/equipment: While the spaceship is flying, the string is very visible. Also, you can see on the bottom of the spaceship/plate that there is a flowery design. (00:04:45)
Revealing mistake: After Clay finally has been killed, you can still see him breathing, and even blinking his eyes.
Continuity mistake: When the stewardess enters the cockpit with her clipboard, she disappears during a closeup on the pilot. It has nothing to do with a different camera angle. (00:29:20)
Plot hole: When the flying saucer first appears, it is supposed to be 4 AM. But the grave diggers are still there from the burial of Bela Lugosi's wife.
Visible crew/equipment: When Colonel Edwards enters the General's office, the moving boom mic is visible at the top of the screen.
Continuity mistake: The co-pilot radios in to Burbank tower in the middle of the night. In the next shot we see the saucer and it's broad daylight. (00:04:30)
Visible crew/equipment: At the funeral scene in the beginning of the movie, the wooden crosses added in the cemetery are obvious props. (00:03:40)
Deliberate mistake: Whenever we see Vampira, they use the same footage, as she's always in the same place next to or near the wooden mausoleum. (01:10:15)
Deliberate mistake: The saucer flies left to right past a church at the beginning of the movie. Later they just reverse the film as the saucer flies right to left away from the same church. (00:05:35 - 00:13:15)
Continuity mistake: As she is chased by the ghoul in the cemetery, Paula knocks over one of the wooden tombstones and you can see the stand underneath that holds it up. The next time we see it two shots later it's been set straight again. (00:32:55)
Continuity mistake: When the flying saucer is seen taking off from the cemetery, it is saucer shaped. However, when it is on the ground the ship appears to be in the shape of a square building. (00:37:05)
