Police officers are generally trained in how to properly handle firearms - yet in several scenes they are seen to grossly mishandle them, such as using the barrels of their pistols to adjust their hats, scratch the sides of their heads and gesture at others, all while their fingers are clearly on the triggers.
It is said that Col. Edwards is in charge of a division of the government specifically for dealing with saucers, yet during their meeting, Gen. Roberts insinuates that Edwards could be in trouble for acknowledging that saucers exist, due to a government directive stating that saucers don't exist.
The gravediggers apparently don't fill the grave we've seen before, they just throw the earth behind them, as if they started to dig a new hole. Still in the same position, their work is then declared to be done and they leave the place. There is no new or any other grave on the scene which is supposed to take place on the cemetery.
Criswell's opening narration (where he can be seen reading off of cue cards) begins: "Greetings, my friends. We are all interested in the future, for that is where you and I are going to spend the rest of our lives. And remember, my friends, future events such as these will affect you in the future." A moment later, though, he is placing the same events in the past, telling how "what happened on that fateful day" must no longer be kept secret. In the next paragraph he says it's sundown when it's obviously broad daylight.
Tor Johnson's character, a police detective, is called "Inspector Dan Clay". Although San Francisco and a few other cities use the title "Inspector" for their detectives, virtually every police department in California - and in Los Angeles, Burbank and San Fernando, where this was filmed - uses the title "Detective".
When the police leave the station house to go to the graveyard, it is night and they pile into a black 1953 Ford. A shot of the police car driving on the road to the cemetery - in daylight - reveals that it has changed into a 1957 Ford (and just before the shot ends the car pulls over to the side of the road and the occupants start to get out, although neither the cemetery nor Jeff's house is anywhere in sight). A few seconds later, as the car pulls into the cemetery, it has metamorphosized into a black-and-white 1956 Ford, and it is nighttime again.
Paula runs out of her house barefoot, but after she is chased through the cemetery and is picked up alongside the road, she is wearing shoes. Immediately afterward, the police discussing her case note that her feet were all scratched up from not wearing any shoes.
Colonel Edwards had three rows of service ribbons when he was briefed by General Roberts. The upper row (a single ribbon) is crooked and ready to fall off. Apparently it did fall off, because in his next scene the upper ribbon is now missing.
When the two military officers are listening to the "Eros" tape, the later cutaway shots of the tape player show the officer's hand resting on it even though in the shots of the officer it's clear that he moved his hand away after turning it on.
When "Vampire Girl" attacks the two gravediggers in the cemetery, she arrives just a few seconds after she's just been buried, and from a completely different direction. She should come from behind them, not the front. To be able to pull this off at all, she'd have to get out of the coffin and tunnel beneath the length of the cemetery at lightning speed.
Paula runs past the same spot on the cemetery seven times while being chased by "The Ghoul Man". "The Ghoul Man", on the other hand, only passes the spot once, but manages to make a headstone sway distinctly while doing so. However, he passes another spot on the graveyard (i. e. they've rearranged the headstones) four or five times.
Someone's hand (either that of the stewardess or a crew member) from behind touches the shower curtain in the cockpit of the plane as the pilot says, "You better radio in for landing instructions, Danny".
The scenes of the military attacking the flying saucers with artillery guns are obviously taken from stock footage of the Korean War. You can even see the thatched huts of a Korean village in the background, even though the action is supposedly taking place in California.
Stock footage of rocket launchers is used to show the attack on the flying saucers, which are up in the air. The rocket launchers are ground-to-ground weapons. Also, one of the rocket launcher vehicles shown is a Russian 'Katyusha' truck, filmed during the Russian counteroffensive during WWII.
The Pentagon has a special computer to translate alien language. Although it's hard to catch, Eros turns on a similar computer on his ship right before the climax, so the humans and aliens understand each other during the final confrontation.
It is said that the Pentagon is in Washington, D.C. It's really in Arlington, Virginia, but is so linked to Washington's political and economic culture and so close physically that Pentagon employees generally think of themselves as Washingtonian rather than Virginian.
The map on the wall of Gen. Roberts' office, which is supposed to be in the Pentagon, is clearly imprinted on the bottom left-hand corner with a large logo of the Santa Fe Railroad. Later, when the General points out something to Col. Edwards on the map, the words "Santa Fe" have been taped over.
When Kelton and the second police officer hit the zombie Inspector Clay on the head knocking him unconscious, he falls to the ground dropping the passed out Mrs. Trent who the zombie captured in a previous scene. As Mrs. Trent falls, pillows placed on the ground to cushion her fall can be seen.
During the first briefing between Eros and "His Excellency", the latter stops talking mid-sentence twice, and obviously has to read his lines from a hidden manuscript on his desk before he can continue.
When Colonel Edwards, Lieutenant Harper and Jeff Trent confront Eros and Tanna for the first time in the flying saucer, white X's, used to indicate the actors' places on the set, are clearly visible on the floor.
Eros forces the heroes to look out the window of the spaceship
to see the Clay ghoul. One window shows gray mist; the window beside it shows complete darkness. In neither window can the Ghoul Man be seen.
In the cockpit scene, the curtain separating the cockpit from the rest of the plane is rustled, and you can catch glimpses of the stewardess behind it. It's obvious she's waiting for her cue, even though she shouldn't be anywhere near the cockpit at that moment.
The inside door of the small saucer is the same as the outside door (there is the same ladder on the left hand side of the hatch). Obviously the exterior walls of the saucer were inverted to provide the interior set. The hatch itself is the same as the hatch on the airplane cockpit, and in the interplanetary headquarters.
The aerial shots of the saucer make it appear to be round, but shots from the ground show it as having straight sides and square corners. One miniature saucer was modified to accommodate the square-sided set (see Trivia entry).