Continuity mistake: When Wednesday and Pugsley are playing with the guillotine, Wednesday has a scroll in her hands, which she then rolls up. The shot changes and you can still see the rolled up scroll in her hands. However, the shot then changes again and you can now see Wednesday rolling up the already rolled up scroll.
Continuity mistake: After Winifred, Sarah, and Mary get off the bus, when the young girl dressed as an angel stops and says, "Bless you," the candy bag she's holding switches from her left hand to her right arm, then back to her left hand, between shots. (00:48:10)
Continuity mistake: In the scene where Jessica is in the shower crying and the power goes out, she gets out, puts on a white t-shirt and goes walking around the house. When she walks through the garage door and grabs a hammer, there is blood on the front of the t-shirt (right at or a little lower than her waist and looks like someone grabbed the shirt with a bloody hand). Where did it come from? She didn't run into anything or anyone. [There's a deleted scene showing her step on a piece of glass. She gets blood on her hands when she pulls the glass out, then presumably wipes her hands on her shirt. Still a mistake, as removing that scene means the blood appears from nowhere, but there's the reason.]
Continuity mistake: After Nathan pours the gasoline and throws the match in the well, we see a canister and shotgun sitting by well. But when the well explodes, they've disappeared. (01:23:50)
Continuity mistake: When Henry & Mark were chased by the dog, look carefully at the back of Henry's jeans and you will see a large dirt stain on it, but in the following scene over the cliff, there is a brief overhead shot over Henry and you will see that stain is gone.
Continuity mistake: At the Riverman's place, Julie grabs a piece of glass from his foot and stabs his left hand with it, later when she is finishing his transformation and stabs a knife in the same hand, there's no sign of the earlier injury. (01:02:50 - 01:04:45)
Continuity mistake: In the prosecuting attorney's speech in the first courtroom scene, the judge's house of cards is no more than 2 levels high (a base level with a peak) [0:2:20]. In the close-up shot of the judge, the house of cards changes to 3 levels high (2 base levels and a peak)[0:2:35]. When the scene focuses back on the prosecuting attorney, the house is back to two levels of height[0:2:39]. (00:02:20)
Continuity mistake: In the scene where Gard telepathically fights an alien, you see his nose bleeding. Then the alien explodes, and in the next shot of Gard's face, the blood under his nose has vanished, only to return in the next shot of his face.
Continuity mistake: When a Totem attacks Cameron in the car, he leaves some blood on the driver door window. The blood disappears and reappears in between shots.
Continuity mistake: Julia is apparently being helpful towards the stranger at the door. She is taking notes as he says his name and auto club card number. She is casting a visible shadow on the door, entirely gone in the close-up of the door itself. (00:08:15)