During the football game, Miller gets called on the field. With the scene shot from ground level, he can be seen to be wearing Nike cleats. After he gets bitten by the spider in his helmet, he falls to the ground, and he's wearing Converse cleats. When the camera turns back to his body, he's wearing the Nikes again.
After the photographer has been bitten by a spider, he lies down on his bunk and dies. He is lying on his left-hand side, dead, when a little blood dribbles out of the left corner of his mouth and runs down an inch or more onto his left cheek. When he is shown in his coffin a few moments later, he still has blood in the left corner of his mouth, but the bloodstain is much smaller and, instead of running across his cheek, it is pointing down - towards his chin.
In the coat hook scene, at one point you can tell a car is passing by the light coming through the window. And by the sound of the engine, it was passing by at quite some speed, but the Jennings house is in the middle of nowhere with no apparent through road.
The first close-up of 'The General' and every subsequent shot of him biting someone shows him with large, jumping-spider eyes. However, every time the real-life spider is shown in full, even close to the camera, his eyes are almost invisibly small.
Towards the end of the film, Ross slams the TV on the floor, but when they all head towards the door moments later the TV can be seen behind them in an upright position.
Throughout the movie, The Queen spider makes several squeals or screams. Such as when she lunges at the professor. Spiders do not make these sounds. Although some can make a hissing sound, But definitely not the sounds we hear. These are simply added for a dramatic effect, and for those who already knew this, a comedic effect.
Near the end of the movie, when Jeff Daniels' character has found the egg sac and is attempting to destroy it, he grabs a bottle of wine, breaks it, and splashes it on the sac to set it on fire. However, wine, being around 10% to 13% alcohol, does not contain enough to ignite. In fact, it would actually make it harder to ignite.
When Sam says to his wife after he's been bitten that he's having a seizure, he should not be able to speak at all.
The swarming spiders, having no reproductive organs, are compared to drones. Among hive insects, reproduction is actually the primary purpose of drones. It's the workers that don't reproduce.
When Becky is screaming after seeing the spider in the shower, you can see her underwear in the mirror reflection.
When Becky is in the shower, the spider slips down her cleavage. When she looks down and screams, you can see a flesh-coloured garment.
When the General is crawling up Ross Jennings' leg at the end you can clearly see the metal rod pushing it along with a hand.
When Becky is in the shower, a spider is walking across the shower rail. A black wire can be seen moving it along and making it jump a bit. Also, when the spider is descending down her body, a white wire can again be seen pulling it downwards.
In the shot were the flaming General is hit with the nail from the nail gun, you can see the wire that's attached through the spider and to the nail. Also, in the following scene, the general goes in a straight line to the nest, diagonally from about floor level, across the room to the ceiling, defying the laws of physics.
In the night scene when McClintock says, "Rock and roll," his glasses have been sprayed with a matte film to prevent reflections of the lights.
As a medical doctor, Dr. Jennings (Ross) should know to use single-use gloves for each patient. But he did not do that when checking the boys in the locker room, going from player to player with bare hand contact, which is inexcusable and indefensible.
When coroner Irv Kendall and his assistant pry open Manley's coffin to perform the autopsy, they grimace at the stench his desiccated corpse emits. However, the crude, makeshift coffin he was transported in is not airtight by any stretch, and would not have concealed odors up to that moment.
When Ross yells for help while he tries to exit the cellar, his mouth doesn't move.
When the three girls are driving away after being warned about the spiders, one of them says "Yo, Dr.Death" yet none of their mouths move.
(at around 1h 27 mins) When the exterminator's truck stops between the barn the house, there is a crew member behind it, between the porch roof and the attic roof.
(at arouns 0h 19 mins) When the dog and cat use the pet door to run away from the spider, theere is a crew member pushing the fake spider out of the door before the crow lands to catch it.
When the spider attacks were being marked on the map, it suggested that the Jennings house was in the middle of town, but when the bird carried the General over to the house, you can see a mountain range in the background with no other houses in sight, suggesting it's in the middle of nowhere.
The doctor removes Margaret from her blood pressure medication stating that her blood pressure was within normal limits. However, the reason her blood pressure was normal, was because she was taking the medication in the first place.
After the General bites Manley and Manley dies, his heartbeat can be seen.