(at around 1h 9 mins) When Zeke hands Marybeth the pen full of Scat, he keeps the blue top in his hand. When we cut from him to Delilah back to Marybeth, the top is on again.
(at around 1h 3 mins) In Zeke's garage, his glasses jump around his head between shots.
(at around 31 mins) When Coach Willis and Mrs. Olsen enter the faculty lounge, they walk to the water cooler. Mrs. Olsen splashes water on her face and getting some of her hair wet. In the next shot, her hair is dry and perfectly brushed.
(at around 17 mins) When Stokely, Delilah, and Mary Beth are outside, Delilah is talking to Mary Beth about Stokely being a lesbian. Stokely then starts putting things into her backpack. From a wide shot we seeing Stokely zipping up her backpack and nothing else is left on the table. The next shot shows Stokely grabbing her cigarettes from off the table.
(at around 1h 28 mins) The amount of blood on the floor in between shots after the alien trips Stokely.
(at around 1h 26 mins) Marybeth asks Stokely how the book Invasion of the Body Snatchers end, Stokely replies, "They get us. They win. We lose." But actually the book ends with the aliens giving up because they had underestimated the human desire for survival.
(at around 1h 7 mins) When Zeke hands out the Scat pens to determine who amongst them may be an alien the blue cap is still on as they inhale from the other end. Now unless they have a huge inhaling capacity there's no way to inhale a whole pen's worth with one end of a tube sealed.
(at around 48 mins) Zeke tells Miss Burke "It's too Hot", yet he's seen clearly wearing a waffle shirt under his dark t-shirt. Waffle shirts are made primarily to keep one warm, so why would he be wearing one under his t-shirt if it's "too hot"?
Zeke says that pelagic animals are sea dwelling but pelagic species are specifically found in the pelagic zone that is neither near the surface nor near the bottom of the ocean. It does not include all sea dwelling animals.
(at around 1h 30 mins) The controls for folding bleachers could be located in the gym if they are operated by a key; Casey does in fact turn a key before pushing the button.
After Stokely's been unconscious underwater for at least a minute, she doesn't even cough after regaining consciousness.
Near the start of the movie, the coach bursts out in anger, he flips over the bench and various items on that bench fall to the ground. In the next shots these items switch places, between cutaway shots.
(at around 22 mins) While the students are walking toward the fish tank to examine the creature, the tank reflects a crew member in a blue shirt.
As Casey and his father are exiting the faculty lounge, a boom mic is clearly visible over the doorway.
(at around 27 mins) When Mrs. Olson tells Casey and Stan that Mrs. Brummel has cancer regarding her dissolving body in the previous scene, a good portion of the boom mic is quite visible at the top of the screen before zooming in on their faces.
(at around 1h 3 mins) Zeke states that Scat, a diuretic, dries out the aliens. A diuretic makes you urinate and must be ingested to work and would not dry out an object on contact. Scat is a desiccant which would dry out an object on contact.