Continuity mistake: In the opening scene, a Norwegian helicopter is flying across the Arctic. The co-pilot is half outside it. From the exterior angle, the co-pilot has a pair of binoculars and is looking directly downwards with the binoculars also positioned directly downwards. In the next shot, from a side angle, the binoculars are suddenly elevated and he is looking directly forward. (00:02:55)
Continuity mistake: When the Norwegian helicopter finds the dog running in the snow, the dog turns around to notice the helicopter, causing some of the snow around him to push upwards a few inches. The shot cuts to the helicopter, but when the shot cuts back, the snow is suddenly almost level with the rest. (00:03:35)
Continuity mistake: After the scene where the Norwegian helicopter chasing the dog through the snow ends, the scene cuts to the research station. The first shot from the research station shows a sign: UNITED STATES NATIONAL SCIENCE INSTITUTE STATION 4. This close-up shows scratching and rotting all over. A few minutes later, as the helicopter arrives at the station, the scratching and rotting over the "4" is no longer there. (00:04:30 - 00:06:15)
Continuity mistake: After the Norwiegans' helicopter has chased the dog-Thing to the American research station, the chopper flies around the station before landing on the ground. Before landing, MacReady is shown exiting the watch tower with a bottle of alcohol in hand. When he exits, the bottle is around his hip area. Then from an angle of MacReady low down, the bottle is suddenly raised slightly up to his chest area. (00:06:35)
Continuity mistake: When the helicopter is circling the research station, the co-pilot picks up a hand grenade to throw on the ground. He picks up the grenade on the bottom row in the middle column. There is no grenade in the middle column from the second row of grenades and no grenade in the left hand column of the top row of grenades. Around 45 seconds later, in the shot after the dog leaps onto one of the researchers, the exact same shot of the man taking the grenade out of the box has been repeated a second time. He takes out the exact same grenade from the exact same row. (00:07:15 - 00:08:05)
Continuity mistake: After the Norwegians exit the helicopter, one of them goes to throw a grenade but accidentally lets go of it, and it explodes. In the shot where the man takes cover during the explosion, the fire clears out and there is soot around the helicopter on the snow, about six feet. A couple of shots later, as the Norwegian stands up, the amount of soot around on the snow has notably increased. (00:08:20)
Continuity mistake: Just a couple of minutes into the movie, Gary shoots dead the crazed Norwegian and the camera returns to MacReady. Now watch closely: When he gets up to help injured Bennings, he and his Jim Beam bottle are covered up to the hilt with loads of snow. But on the next shot, a split second later, his clothes are miraculously clean and the whiskey bottle as dry as you can possibly get it. (00:09:00)
Continuity mistake: When MacReady and Doc are examining the abandoned shack, MacReady comes across a portable video unit and MacReady then wipes off the snow and dust off the unit. From the first shot of the unit, we can see part of the unit is wiped so far, we are able to notice the unit itself. The visible part of the unit is located in the middle of the unit at first, but after Doc states the papers are in Norwegian and the shot cuts back to MacReady, it is now the edge of the unit that has the top of the unit visible. (00:20:00)
Continuity mistake: MacReady and Doc return to the research station from the abandoned shack in the helicopter. The scene then cuts to the dog watching the two exit the helicopter in the window. In the shot where the helicopter is visible in the window, the dog is looking out of the window from the right hand side. In the next shot, it is suddenly looking out of the left hand side. This mistake has nothing to do with the angle of the camera. (00:22:35)
Continuity mistake: When the stray dog is placed in the cage with the other dogs and starts to mutate into The Thing, one of the other dogs start biting a hole in the fence. We get a clear view of the hole in one close-up, and in the next shot as The Thing sprays liquid on the dog, and the hole in the fence is much bigger. (00:27:45)
Continuity mistake: Just after MacReady overhears the dogs barking, he runs over to the fire alarm, breaks the glass with his beer can and pulls the fire alarm. After he breaks the glass, there is a piece of broken glass located next to the alarm. But in the next shot, as he removes his hand, the piece of glass has vanished. (00:30:10)
Continuity mistake: When the dog, aka the The Thing, is led into the dog pen for the first time we see the floor is covered in a thick layer of straw for the dogs to sleep on. This is seen every time except when Childs uses the flame thrower. We get a wide shot of the pen as it's lit up in flame and the floor is now completely bare of any straw. There are also none of the recently deceased dogs that were lining the floor, being converted into Things. (00:31:05)
Continuity mistake: When MacReady and the two other researches first discover the the spacecraft, there is a shot where the camera is in front of the three looking downwards into the hole. All three of them have their hands by their sides. In the next shot, the researcher on the left suddenly has his arms raised with binoculars suddenly in his hands. (00:38:20)
Continuity mistake: After MacReady and Doc have discovered the spacecraft, the scene cuts to a wide angle of them approaching one of the researchers looking into a dug up hole. Just as the wide shot ends, MacReady and Doc are standing right next to the man. The shot then cuts to a closer angle of the three and MacReady and Doc are now several feet away from him. (00:39:50)
Continuity mistake: Back at the research station, the researchers are looking at some debris from the spacecraft that is placed on a cloth on a snooker table. There is a guy with a grey sweater with his hands in the debris and a guy in a brown jumper also holding the debris. In the next shot, neither of their hands are located on the debris or cloth. (00:40:50)
Continuity mistake: When Windows breaks the glass to the gun cabinet, he takes out one of the shotguns and picks up some ammo. At the left hand side of the cabinet, there is some remaining glass in the cabinet along the side. The glass along the left side vanishes when Windows places the shotgun on the floor. (00:59:15)
Continuity mistake: When MacReady says they are going to find out who's who, he tells Doc, Garry and Clark to move away from the others and one of them steps forward in MacReady's direction. MacReady then raises his flamethrower around the top half of his abdominal region. The shot then changes where the camera is in front of MacReady and the top half of his abdominal region is shown, but the flamethrower is nowhere in sight. The camera cuts to an angle behind MacReady and the flamethrower is back. (01:02:10)
Continuity mistake: When MacReady is recording the stuff he knows about the thing, a glass of alcohol is on top of the tape recorder, located near the front of it. The camera then changes to a close-up of the recorder and the glass is now near the back of it. (01:04:00)
Continuity mistake: Just after MacReady leaves Fuchs to do his work, there are several items on his desk, such as a lamp, conical flask and books. In the first shot shown after MacReady leaves, the lamp is about a foot away from the conical flask and the conical flask is a foot away from the books. Next shot, the lamp, conical flask and books are more closer to each other. (01:05:10)
Continuity mistake: MacReady leaves the room so Fuchs can continue to do his work. The shot changes to an angle from behind Fuchs where he is shown writing on his paper. There is a conical flask visible at the back of the desk with some blue liquid in it. In the next shot, the liquid in the conical flask is suddenly just clear liquid. (01:05:10)
Answer: Remember that he'd just spent the whole day investigating how something mysterious and horrible destroyed the Norwegian camp, so he's already in a spooked state of mind. Hearing the dogs screaming at night is already unusual on its own, and also reminds him how this whole episode all started with a crazed Norwegian trying to kill a dog. Deep down he knows whatever happened to the Norwegians is now starting at their own camp.
TonyPH