Blooper

As Forrest Tucker is talking on the wall phone, the watch on his left wrist appears and disappears throughout the scene.

The jet bomber at the end of the film is an English Electric Canberra, except for one shot where it mysteriously becomes a late-model Gloster Meteor jet fighter.

The bomber is supposed to be attacking a remote mountaintop installation, but the bomb release is shown using stock footage from WWII showing a large city below.

After Brett drinks a glass of wine, the glass is half full in the next shot.

In the train scene early on Forrest Tucker is reading a fresh, crisp, unwrinkled newspaper when Janet Munro has one of her bad spells and falls in his lap. As she falls, Tucker's newspaper looks like it has gone through a few takes already.

When Philip is hauled aloft by the creature Alan throws a molotov cocktail and it clearly bounces off Philips head on its trajectory towards the target. Quite dangerous as it was in flame.

The so-called observatory has two small telescopes behind a large picture window, which would render them virtually unusable.

When turning from the room window after checking in Anne turns and referred to Sara as Clara.

Switzerland did not join the United Nations until 2002. Alan Brooks would have had no authority there in 1958. The British bomber used in the finale would have had to come from West Germany or some other country where NATO was stationed and was also a U.N. member during that time. There was no time to arrange clearances. Technically the act of a warplane entering another country's airspace is an Act of War. The plane should have been Swiss Air Force instead.

After Brett gashes his forehead in a fight, they discover he does not bleed and that he is already dead. Yet Professor Crevette gives Brett an inject-able sedative in the arm. No blood means there is no way for the drug to travel to his brain.

The waiting room at Trollenberg train station is labeled "Wartsaal". The correct German spelling would be "Wartesaal".

At the beginning of the film, while the two mountain climbers are lifting Jimmy up by a rope, the one in the beige sweater is seen pulling on the end of the rope that is not attached to anything.

When the two men from the search party reach the site where they find Brett's bloody pack, one man calls to the other, "Comen ze here, schnell!" This is a poor attempt at saying "Come here, quick!" in German: the correct pronunciation is "Komm schnell her!"

When Alan is going to try out the Molotov cocktail on the monsters, he tells everyone in the hallway to move to the far end, except for one thin man with a gray jacket and hat. He tells him to close the door after he gets outside. Apparently the man has trouble closing the heavy door because a balding crew member wearing a white shirt closes the door after Alan.

Near the end, when Philip is being lifted up by the crawling eye with its tentacle around his neck, it can clearly be seen in the long shot that a tiny bendable doll is used instead of the actor or a stuntman.

Trollenberg isn't in Switzerland nor in the Alps. The travel posters in the Trollenberg train station depict the Matterhorn probably as seen from Zermatt, Switzerland. Trollenberg, however is actually located in Germany's Black Forest, nearly 400 KM away. The closest rail station access to Trollenberg is in Loßburg about 4 KM away. Zermatt, however in the shadow of the Matterhorn, does have a train station and cable gondola service to Furi and Schwarzsee.

The British bomber almost scrapes the top of the observatory building twice making its run.

Though supposedly at the top of the Swiss Alps somewhere, no ones breath outside has visible condensation.

Brett's body dissolves when put close to the lamp. However, he lit and smoked a cigarette at the bar earlier.

A few minutes from the end of the movie, after the shutters on the windows are opened, there is a huge shadow of a boom and microphone on a wall to the left.

When the two men are in the cabin, the door is frequently left open even though it is below freezing outside.