In the scene where Steve is speaking with (sweet) Jeff on the telephone about the "earthquake": In the kitchen window-sill, there is a red pot-plant. Then, the pot-plant is gone when Diane laughs about Dana giving the construction-workers rude gestures, and also when Bluto is drinking coffee and eating biscuits.
When Diane asks Carol Anne about the "TV" people. After the glass breaks and Dana runs out of the kitchen, you can see the boom mic reflecting off the picture frame behind Diane. NOTE: Upper left of Frame.
When Tangina is talking to Diane and the others about Carol Anne she tells them that she can only hear her mother's voice, but in the next scene she tells Steven to threaten to spank her if she doesn't answer them.
Dr. Lesh asks "Where was Carol Ann playing when she disappeared?" to which Diane responds (incorrectly) "her bedroom closet." The last time Diane - or anyone - was in the room with Carol Anne before she disappeared, she was sitting in her bed, pulling her covers up.
After Carol Anne's abduction, when he brings the parapsychologists to the house for the first time, Steve tells them that they keep the kids' room locked at all times and is seen using a key to unlock it when showing it to them. Yet later Diane is seen briefly opening the door without using a key.
When Tangina asks Ryan to take up the slack on the rope, he is seen wrapping the rope around his forearm. In the very next scene when he is holding the rope, the rope is no longer wrapped around his forearm.
When Robbie is sent away and put in a cab, he and the dog seem
to change places between shots. Furthermore, whilst the dog clearly gets in the back seat of the taxi, in the next shot it is sitting in the front seat.
Carol Anne holds onto the headboard to keep from being sucked into the closet. She clearly loses her grip on the headboard and lets go. However, the next shot of her sailing through the air toward the closet shows her holding a piece of the headboard.
When the paranormal investigator takes his face apart in the bathroom, the reflection in the bathroom mirror changes three times: 1. The walls in the reflection are pegboard, and a bottle of "Fantastik" cleaner hangs near the mirror. 2. After a cut to an overhead light and back, the walls are no longer pegboard, the bottle has disappeared, and a cleaning brush has appeared on the wall. 3. After a cut to the sink and back, the bottle is back, but is of a different type, and a black cloth is hanging over the brush.
Early in the film, when Diane tucks the kids into bed, there is a green mylar balloon in front of the window. During the subsequent scene where Robbie covers the clown doll with the Chewbacca jacket, the balloon is in the corner behind the clown doll. Then, minutes later, when Steven takes Robbie back to his room, the balloon is back in its original position in front of the window.
As the abduction of Carol Anne starts, a toy carriage is pulled and falls over a foot away from the closet door. Later, as we see more toys being pulled into the closet, the carriage is at the side of Carol Anne's bed.
The mattress on Robbie's bed changes to a different one during the abduction of Carol Anne.
When we see the hole for the pool as Steve is trying to get Robbie out of the tree, there is a section of the pool on the far right side that is damaged. When Steve goes into the pool to look for Carol Anne the same section is undamaged. Later when Diane runs by the pool to get help the section is undamaged, but just before and right at the spot where she "falls" into the pool, the section is damaged in a way that suggests multiple takes at that spot.
When Carol Anne is feeding her fish, her bed is "neatly" unmade, but when we see Robbie looking at the tree from the outside, we see that Carol Anne's bed is made. Finally when Diane comes in and tells Carol Anne not to feed the fish that much, Carol Anne's bed is "dramatically" unmade.
In the beloved breakfast scene with Diane and the kids, Diane's spatula appears and re-appears. When Robbie first says "Ask Dad!", Diane's right hand is firmly clasped around the plate of waffles. Then, in the next shot, she has the spatula in her hand again.
In the breakfast scene: When Diane is speaking with the kids about Carol Anne saying "They're Here", the chair to the right of Robbie is pushed to the table. Then, when Carol Anne runs around the table to watch TV, the same chair has moved out from the table.
At breakfast: In the shot where Robbie is offering E.Buzz a waffle underneath the table, there is no chair next to Robbie's immediate right. Then, in the subsequent scene of Diane and the kids, there is a chair besides Robbie.
At the end of the film, Steven backs out of the driveway in the station wagon without lights on and crashes into Mr. Teague's truck, yet in the next shot, still pushing the truck out of the way, the wagon's lights are suddenly on.
When Carol-Ann get's abducted there is a Darth Vader poster hanging on the right and an 'Alien' poster on the left of the closet door. During the scene the Darth Vader poster moves from hanging on the wall, to getting blown around the room (next to Carol-Ann's bed) to hanging back on the wall again. The Alien poster goes from hanging perfect, to flopping around an almost falling off the wall, to hanging perfect again.
During the storm and the parents and two kids are in the parents bed you see two white pillows in the background one standing upright and the other leaning on it, you can see the leaning pillow go from leaning to straight up and back and forth several times. (time index 21:56, 23:27, 23:37)
When Dana looks out the window at Steven rescuing Robbie from the tree, it is raining against the window and dark. In the next shot, she runs outside to witness the tornado vanishing and the rain has stopped and it is much brighter outside.
When Diane calls Carol Anne in the living room, this one answers "hello daddy" in presence of her family in addition with Dr. Lesh and her assistants Marty and Ryan. Seconds before of the Carol Anne's answer Ryan appears in background on bended knee, putting his hands on his headphones, but when the camera focuses Ryan, he puts his hands on the headphones again.
When Diane returns to the kitchen to find that all the dishes have been put away, she is startled when Carol-Anne tugs on the back of her T-shirt. This is obviously a second take since Diane's T-shirt already has an impression in it at the very point that Carol-Anne tugs.
Diane is shocked by the front doorknob, when trying to escape to seek help. When she is thrown across the room, behind the staircase, a crewmember's foot can be seen pulling back suddenly in an (unsuccessful) attempt to stay out of the shot.
When Diane is pulling Steve into the house right before the chair sliding scene, the garbage can Steve is holding onto gets stuck in the doorway. The hand and shadow of a crew member is clearly seen grabbing the can as Steve lets go.
As Ryan is sitting by the monitors listening to music, the camera starts moving. When it comes to the point of facing straight towards the viewer you can see the camera used to film the scene and some of the lights on the set.
In the opening shot immediately following the credit of "Directed by Tobe Hooper": Jeff Shaw on the bicycle pulls out of his drive-way (at the end of a cul-de-sac) on a bicycle with a crate of beer under his arm, and he turns left. Opposite the cul-de-sac is a yellow van parked in it's driveway. However after he turns left, there is no yellow van and the texture of the lawns are completely different. It is a different street.
The second floor of the Freeling's house is completely inconsistent with its exterior. From outside a large window is seen above the front door, but inside is a vaulted ceiling above the front door and the window is not there. Strangely, this window appears only once behind Diane while she's running down the "corridor" to Robbie's and Carol Ann's bedroom, yet this too is impossible because the upstairs hallway isn't above the front door.
While attempting to photograph the flashing lights, Marty (Martin Casella) the paranormal investigator, takes two shots with the camera making two obvious auto-film advance sounds, this despite not having any film motor drive attached to the camera body.
During the initial investigation, when the ghost comes down the staircase, nothing appears on the monitor, but when reviewed, the tape does appear to have captured the incident. This is part of ghost lore.
Before Diane takes a bath, Robbie and Carol Anne are fighting over a toy truck. Carol Anne is holding onto the truck saying "Gimme it!" to Robbie and jerks the truck towards herself as if Robbie is holding onto it, but he isn't holding it at all.
In the beginning of the movie, Steve is watching a live football game on TV with his friends. Despite their reactions to the live game, the game play on TV is in slow motion, making it previously recorded footage.
At breakfast, the glass that is about to break in Robbie's hand is leaking considerably, but the amount of milk in the glass is unchanging (considering how much milk is leaking and how much is on the table already).
When Marty goes into the bathroom after seeing his steak ooze and maggots on his chicken leg (which he drops on the floor). He goes into the bathroom and starts pulling the skin off his face - clearly a dummy was used for this scene.
In the kitchen chair sliding scene, Diane fails to place the front legs of the chair within the white circles that have been drawn. The front right leg (the viewers left) is also not placed on the line separating the tiles as it appears in the following scene when the chair actually moves. After Diane moves away from the chair, the chair's front legs have been miraculously aligned with the white circles and the front right chair leg has been placed on the line separating the tiles. This indicates that there were multiple takes and most likely a mechanism between the tiles which helped the chair to move.
The goof items below may give away important plot points.
A community with foundations, basements and a swimming pool or two, was built on top of buried bodies. With the standard grave being dug only six feet into the ground, the bodies should have been discovered much sooner by the community's builders.
At the film's climax when the family piles into the station wagon. Robbie is seen wearing blue pajamas when he screams, "Daddy, drive away!" After Dana gets into the car, Robbie screams "The house is coming!" This time he is in the red pajamas from the previous scene.
The family is loaded into the car at the end of the movie, and the dog gets into the front seat. The dog then disappears while Steven frantically obtains his keys, and reappears back in the seat in the next shot as Steven climbs into the car.
In an extreme wide shot of the Freelings' house just before it implodes, Teague is seen with his hands defensively raised above his head. In the next shot his arms are at his side. In another shot he is blown down to the ground by a funnel of energy, the next shot is a side view of the street where Teague is no where to be seen.
Towards the end of the movie when the kids are almost eaten by the giant esophagus, you can clearly tell that a dummy has substituted for Carol Anne due to the fact that Heather O'Rourke was too frightened to do the scene (see trivia). The positions of the dummy and the real Carol Anne change between shots.
When Diane encounters the beast in front of the door and yells "Nooo, don't touch my babies!" she crosses in front of it and falls down the stairs. As she passes in front of it, the creature's eyes and mouth can be seen on the front of her shirt.
When Steve arrives at home to find the caskets exploding out of the ground at the end of the movie, in one shot shortly after he arrives, we can see an explosive charge detonating to create the proper exploding dirt effect shortly before another casket emerges.
Near the end of the movie when the house implodes, the lights on the pillars adjacent to the front walkway stay lit. In any normal house these lights are connected to the house's electrical system and would have gone out as the house is destroyed.
Diane is trying to rescue her children from their bedroom where a giant esophagus is sucking everything up and the children are clinging to the headboards of their beds. When she pulls them out an overhead shot in hallway reveals they're now simply running out and falling to the floor.