When Hopper comes to talk to the boys, Dustin has headphones on for the HAM radio and takes them off. In the next shot, they are on his head again.
When Karen picks up Holly and leaves the dinner table, she also picks up Holly's cup. When the shot changes showing Ted sitting at the table, the cup is back on Holly's highchair.
When Hopper picks up Will's bike in the forest, the front light is visibly broken. When he returns the bike to Will's mom, the light is undamaged.
When Mike is upstairs talking to his parents, his hairstyle changes with each new angle.
When principal Coleman comes into the AV club to get Michael, Dustin, and Lucas, Lucas had just pulled the headphones off of Dustin's head. In the next shot Dustin pulls them off of his head again.
In the opening shot of the Wheeler's house, a sprinkler can be seen watering the grass. In early November, it would be way too cold for this, and instead the outdoor spigots would be shut off and drained to prevent them from freezing.
In the biohazard containment area, people are donning their Tyvek suits with their gloves and boots on top of the Tyvek, then putting on duct tape. That's a major no-no, especially in a highly hazardous environment. The proper way is to put sleeves over gloves and cuffs over boots, then those locations. They are also shown not taping the tops of their boots, which would make the whole process useless.
When Will runs away from the Demogorgon (and thus, his bike), the camera is close on his bike's still spinning rear wheel making a noise. The noise used is from a bike with gears, but his bike has no gears and shouldn't make such a noise, if any.
At the beginning, we see the kids switch on their bicycle lights, including Will. The lights on their bicycles are Miller or Miller style lights that used a generator that ran off of a bicycle tire and no batteries. The Miller style lights illuminated as you started moving. The faster you pedaled, the brighter the light would illuminate. There are no switches on the lamps, which is obvious in later scenes.
A few minutes after this scene, there is a close up shot of Will's rear tire, including the electrical generator for the light, and the wire running along the frame up to the light. The generator is in the 'off' position and is not contacting the tire. The generator would have contacted the tire on the side near the rim when operational.
A few minutes after this scene, there is a close up shot of Will's rear tire, including the electrical generator for the light, and the wire running along the frame up to the light. The generator is in the 'off' position and is not contacting the tire. The generator would have contacted the tire on the side near the rim when operational.
When wearing the "astronaut" suit, Dr. Brenner and his crew seal the gloves against the sleeves but the boots are not sealed, they use regular white rubber boots.
Joyce presents her son Will with tickets to Poltergeist. The original Poltergeist came out in the summer of 1982, almost a year and a half before the events of the show. It's unlikely the film Poltergeist would have still been playing at theaters, however this is clearly a flashback to earlier events that Joyce is remembering which could easily have taken place when Poltergeist was still in theaters. The flashback is not time-stamped.
Some may think that none of the Dungeons & Dragon figures are painted, but this is not true as some such as the demogorgon, dwarf, and barbarian used. Even if none were painted, however, at the time most miniatures sold by Grenadier, TSR, and other manufacturers were completely unpainted. Often times, people would paint the miniatures themselves. Even so, showing miniatures unpainted at this time is not a goof.
Chief Hopper is wearing the wrong US flag patch on his right shoulder. The field of stars is pointing backwards instead of forwards. That flag patch is for the left shoulder. (min. 25)
The headset that the group are using with the Heathkit sports a CE mark, which were not conceived until 1985.
At 02:51 -the Foley artist has gotten a bit carried away. Dice will not make a clattering noise on carpet.
Begins with the date of 6 November, 1983, which was a Sunday. When the boys are finishing their DnD game, Mrs. Wheeler says "It's a school night", and Mike said they had been playing for 10 hours, which also indicates that it was a Sunday. For a brief second, Mike's father is shown trying to improve reception on the TV, on which Knight Rider (1982) can be seen. In the Fall of 1983, Knight Rider was on its second season, and indeed the appearance of KITT's voice box seen on the TV appears to confirm a second season episode is showing. However the dialog barely heard does not appear to come from K.I.T.T. the Cat (1983) that aired that night.
The flag seen on numerous flag poles underneath the US flag is the 2003 Georgia state flag. In 1983, the Georgia state flag still contained the Confederate battle flag.
During the Dungeons & Dragons gaming session, the Grenadier Miniatures figure of Demogorgon makes an appearance. The events of Stranger Things clearly take place in 1983, a year before this figure was produced in 1984.
The watch Dustin wears (in 1983) is a Casio F-91W, introduced in 1991.
The periodic table of elements on the wall of the science classroom includes elements discovered/synthesized after the time in which the show is set.
Near the beginning of the episode, shown as 6 November 1983 (a Sunday), Mike's father can be seen trying to fix the reception on the TV while an episode of Knight Rider is visible. While Knight Rider did in fact air Season 2 episode "K.I.T.T. the Cat" on 6 November 1983, the dialog heard between KITT and Michael during that brief shot are not part of the episode that would have aired that evening. KITT can be heard saying "very hard" while Michael Knight says "I don't want to hear it". Those lines are not in the "K.I.T.T. the Cat" episode.
Right after a flashback of Joyce telling Will he could see the film Poltergeist, when Joyce was peering into the fort and stepped back, a man can be seen jogging in the background.
In the forest scenes, we repeatedly see long leaf pine trees. There are no such pines anywhere within 300 miles of Indiana (but are very common in central Georgia where the episode was filmed).
In no part of Indiana would tree leaves be green in November. Nor would it be warm enough in the morning for Chief Hopper to step outside bare-chested.
The setting of the story is supposedly in Indiana. However in the opening scene, we see a car with a license plate that reads 7f a xxxx. From 1950 to 2008, Indiana license plates always started with a one or two digit number which was a county code that corresponded alphabetically to the county of issue. For example, Adams County would be 1 a 1234 whereas Wabash County would be 85 a 1234. Given the time setting of 1983, that license plate would have been impossible in the state.
No one thinks to alert the FBI / Kidnappings & Missing Persons.