Plot hole: There must be a lot of dumb scientists in Sebastian's lab. While defibrillating the invisible gorilla, (s)he becomes completely visible for a moment. However, not once do the scientists consider that applying a mild electrical shock to the system renders the invisible animal visible again - that electricity may be the key to the whole invisibility problem. They don't even comment upon the fact that the gorilla does become visible.
Plot hole: Spoilers. It's revealed that the barn game takes place at an old farmhouse owned by the family of Jill Tuck - Jigsaw's widow. It's public knowledge that she was married to Jigsaw and that buildings they owned served as the headquarters of several past traps, so the barn should have been investigated at some point in the meantime. Ten years have passed. It makes no sense that the barn was never investigated and that the bodies of the barn victims were never discovered.
Plot hole: Anubis Warriors can only be killed by being beheaded. But during the final battle, you see several are killed by simply being stabbed.
Plot hole: When Andy turns into a werewolf, he kills both Amy and Detective Benbou. Later in the morgue, Amy tells him because of this that she is forced to become his "rotting sidekick." If this is completely true, then Detective Benbou should also be following Andy around but he isn't seen after Andy manages to escape from the morgue.
Plot hole: The whole problem with the teleporter occurs when fly DNA is mixed in with Seth Brundle's DNA, starting his transformation into the Brundlefly. Brundle is on a hiding to nothing from the word go, and the fly is irrelevant. Humans are a walking talking mass of foreign DNA - we are host to one trillion bacteria all of which has a complete complement of DNA, as do various tiny mites that live in our hair follicles and all sorts of single cell organisms in our gut. If the transporter serves to mix the DNA of all living creatures which are in the transporter pod at the time Brundle would turn into a half-man, half-bacteria. Incidentally, DNA from a bacteria, an amoeba or a hair follicle mite would be just as 'compatible' with human DNA as that from an insect. It's quite a simple chemical, really.
Plot hole: When Bridgette ran through the glass and Linda and Jim were at the hospital Jim tells Linda he called her mom and told her what happened and she was coming to stay over the next day. Yet apparently her mom forgot what happened because she had her committed because Linda didn't remember what happened to Bridgette's face. Also, Bridgette was like 9. How come no-one just asked her what happened?
Plot hole: Peter goes into Carl's mind to save Catherine. When he's in there he sees the tank with the water nymph. On the tank are strange symbols which provide the FBI with the clue needed to find the latest victim. Makes sense so far. But, go back to the scene just after the FBI have captured the comatose killer and are looking in his basement. The FBI are looking at the contraption that the killer uses to suspend himself over the victim. On the contraption is the same symbol seen later on the water nymph's tank. Why didn't the FBI follow up the symbol then?
Plot hole: When the cop shows Pam the newspaper clippings they include what look to be fresh photos of the real Jason from the events of Part IV, yet no photographer is ever seen taking pictures of Jason alive in the previous films and most likely wouldn't live long enough to publish the photo. (01:25:00)
Plot hole: The spinosaurus manages to smash through a metal reinforced wall designed to stop dinosaurs getting past it without too much effort, yet it can't get through a wooden gate secured by some metal bars. It makes no sense.
Plot hole: At the angle of descent and the speed it was traveling (still burning from reentry even), when the space shuttle crashed in the opening of the film, it would not have left much of anything behind. The kinetic explosion that would have resulted would have downed the forest around it for a good distance leaving a crater, and the clean up crews would have been lucky to find any piece of the ship itself still intact bigger than a football. Much less been able to find any discernible remains of the crew. Yet bodies were being taken out in still relatively good condition. And probably most unbelievable is that the glass containers holding the Symbiotes were not even broken.
Plot hole: After Max and Allison rescue Dani from the witches, Max is driving his parents' car. Winifred flies up along side of them and asks Max to show her his driver's permit. How would she know about driving permits, since she's been dead for 300 years?
Plot hole: It's never explicitly stated or shown that the Thing reproduces with each victim until the movie is nearly over (when Palmer infects Windows). Most viewers figure it out from the context, but it's unclear just when and how the characters themselves have come to this conclusion. This was an inadvertent result of an editing decision and a visual goof: there is a deleted scene in which Blair explains much more directly that the Thing multiplies according to how many victims it takes, and in its place in the final film is a scene containing a computer simulation that director John Carpenter acknowledges was a failed attempt at explaining the organism's life cycle.
Plot hole: We see Michael wearing the mask throughout the day, from morning at the Myers House, to mid-day outside Laurie's school, to afternoon when Tommy is leaving school, yet when Laurie and Annie see the sheriff in front of the hardware store on the way to their babysitting jobs (presumably in late afternoon or early evening), the store's alarm is still ringing and the sheriff mentions that one of the items stolen was a Halloween mask.
Plot hole: Through this film (and its predecessor) it is established that the creature imitates its victims perfectly, having all of their knowledge and memory. At the end, when the female lead tells the male lead she knew he was human because of his earring, he reaches for the wrong ear, confirming he is The Thing. Even if The Thing couldn't reproduce the earring, it would have known which ear it was supposed to be in.
Plot hole: When the first security guard, who stayed back to get something to eat, hears something in the laundry room, he walks over to the washing machine where he finds the head of the other security guard inside. He turns around screaming and trips over the security guard's body on the ground with no head. Wouldn't he notice the dead body on the ground when he first entered the room?
Plot hole: Det. Kerry says at the scene of Paul's trap, "He had two hours." There is no way she could have known that. The clock simply said 3:00 and the tape specifically says "you have until 3 o'clock or this room will become your tomb". No way to know that's two hours after the fact. (00:17:30)
Plot hole: Laurie calls the police from 1987 Winchester drive, and gives them that address. Yet the police responding to the call go directly to 1960 Winchester drive - where Laurie has run to and is now hiding - even though it's on the other side of the street and several houses down. (01:31:30 - 01:33:40)
Plot hole: In the end of the film it is heard the police want to exhume the body of Charles Lee Ray from his grave site in New Jersey. Now when Chucky and the crew get to the grave site they find and kill a coroner who is digging up the body. He is the only one there at 1am, by himself, a lonely coroner without any police officers, after all this is a police investigation and I doubt the cops would have him there alone. Then right at the end the Detective who is hunting them arrives. Now he is a cop from Lockport, about six states away. A. Why did he drive all that way to see the body? B. A cop from all the way down there shows up but no new Jersey cops are at the scene?