Continuity mistake: In the scene where the townspeople are fleeing to the mall there is a shot of the Deputy driving the car. You can see the top left hand corner of the windshield is covered in green goo, but when you see them parking the windscreen is completely clean. (01:03:35)
Continuity mistake: When the townsman flees the Diner and gets into his car to flee, the front car window is wound up. The next shot of his face clearly shows the window wound down yet his hands have been busy starting the car all the time. (01:01:10)
Continuity mistake: In the scene where the spiders are starting to attack the city, it shows the guy in the barber shop closing up. He shuts the blinds then his friend gets attacked by the spiders, then he goes back out in front and the blinds are still open. (00:51:00)
Continuity mistake: In the bedroom scene where the sheriff goes in to talk to her son, the movie "THEM" is playing on the TV set. It pans back and forth a couple of times throughout the scene from mother and son to the movie on the TV and the scenes from "THEM" are all out of sequence. (00:30:40)
Continuity mistake: When Chris' Aunt Gladys is searching for her missing dog (it went looking for strange noises inside a wall) her cigarette is burnt out. After a change of the camera angle, she smokes a fresh cigarette. (00:43:50)
Other mistake: Every person in the movie has exactly the same make and model of computer with exactly the same desktop configuration on it. The number, type and order of icons is the same, as is the plain blue background. (00:30:50 - 00:31:40)
Continuity mistake: Towards the end when Chris and Gladys escape the giant spider in the mine on a motorbike, Gladys picks up a helmet and says to Chris, "I need this more than you". The helmet she is holding has a cobweb on the cage at the front. But once she gets on the bike with Chris, the cobweb has disappeared.
Audio problem: In the scene where all the towns residents take refuge in the Prosperity Mall, the mall's janitor/caretaker guy says something to the female sheriff with the camera facing him. In mid sentence the camera angle changes to behind the janitor but at an angle - you can hear him keep on talking but you can see that his jaw is perfectly still meaning that he can't possibly be talking. (01:11:25)
Continuity mistake: The sign on the door that was blocked by the fork lift truck gets half knocked off by a spider; then you see it intact. (01:20:55)
Visible crew/equipment: In the beginning of the movie, when the kid goes for the first time to the spider farm, you can see the camera and crew reflected on the glass of the spider tanks. This is seen when the kid is looking for the owner of the spider farm among the tanks.
Continuity mistake: Something weird happens as the sheriff rolls under the closing gate. She's holding a shotgun before she drops to the floor, rolls under with empty hands (seen from both sides), and as she stands up she's got it back. What's weird is that her dropping and rolling is one continuous shot, so she must have deliberately thrown the gun offscreen as she fell to help her fit through the narrow gap. She doesn't throw it through the gap - we'd be able to see it on the other side. (01:02:40)
Revealing mistake: When the boy runs from the jumping spider he crosses the road, which makes the eighteen wheeler lose control and it jacknifes. You can clearly see a set of tyres are moving with the right direction of the truck, and there are a set of tyres sliding. (00:40:55)
Continuity mistake: In the scene where the developer goes out to check his ostriches, his flashlight changes size. It goes from large to small, then back to large. (00:33:05)