Audio problem: When the cop saves the girl from the mob of locals, his car tires squeal as he accelerates away, but the car is on loose dirt, which makes the squealing impossible.
Revealing mistake: When the scientists inject the mouse with poison, they put it in a jar. The, after they place it down you can see someone's hand swap the jar for one containing a dead mouse. You can even hear it. (01:17:58)
Continuity mistake: Just before the giant tarantula attacks the house where heroine Mara Corday is studying, you can see several book on the library table at the big picture window. The largest book on the table keeps shifting positions in several scenes.
Continuity mistake: When Fin stops near the school bus, the bus number changes from "278146" to "278245" during the rescue of the kids.
Factual error: In the cemetery, the skeleton of Gregory Peck's son is far too big to be that of a newborn, which it is supposed to be.
Revealing mistake: When Louis gives Gage the lethal injection, because the syringe is transparent you can actually see the prop needle retract in and out of the syringe as he supposedly injects Gage.
Continuity mistake: When Trent and Bree are having sex, the ceiling fan is on then off.
Visible crew/equipment: When the Hitchhiker was thrown out of the van and chases after them the camera cuts to the inside of the van and a crew member wearing a red T-shirt and clapper board are visible reflected in the window from the inside view.
Visible crew/equipment: In the second scene where the main character approaches the car, there's the filming crew visible in the right corner of the car's bumper. (00:02:30)
Revealing mistake: When the man pushes Leroy's body down the basement stairs, as his body is sliding down, when it's almost to the bottom, you can plainly see Leroy lift his head up as he's sliding, although he's dead.
Continuity mistake: When Amber and Jonesy get an arrow through the head, the cannibal was on Jonesy's side, so the tip should have gone through Amber's head, not Jonesy's.
Revealing mistake: When the killer is attacking Cici on the balcony, you can see blood on Cici's back before she is even stabbed and both times she is stabbed, the knife that comes out of her back has no blood on it. (00:33:20)
Revealing mistake: When Bert is running in the woods, away from the local guys, he rubs blood on a tree to make them believe he ran a certain way. Look close, the tree already has red tint on it probably from previous takes that didn't wash off. (01:04:35)
Revealing mistake: In the library scene when Richie sees Pennywise the clown, all the balloons filled with blood are popping on people who aren't supposed to be able to see them, but one lands on a lady and you can see her jump as the balloon pops.
Continuity mistake: A blond boy in a light brown shirt is attacked by a crow and goes from having no blood on his neck to having a lot of blood smeared on his neck between shots. (01:14:10)
Other mistake: Max says that Michael is the "Man of the house" and won't come in until he's invited, which Michael sarcastically does, except Michael isn't the man of the house - its actually his grandfather who owns it.
Continuity mistake: When the car door is ripped off by the cow, it shows the truck with the door intact.
Other mistake: When everyone is looking for Bobby, Matthew Lillard says that it is no use shouting because the glass is 100% sound proof. Yet when he is trapped in the cage, he hears Maggie screaming directions for him to dodge the ghost - not sound proof at all then.
Continuity mistake: In the scene where the Nemesis kills the 13 S.T.A.R.S members, after it blows up the sniper on the roof an additional S.T.A.R.S member can be seen outside the building on the right who wasn't there earlier. He then disappears shortly afterwards.
Continuity mistake: When chasing Jamie in the woods, Mikey's headlights go from normal chevy headlights to off-road high beams.