Chapter Seven: The Bathtub - S1-E7
Continuity mistake: Steve has a Coke can he holds to his face. The can moves around each time the shot cuts.
Chapter Two: The Weirdo on Maple Street - S1-E2
Factual error: When Chief Hopper and his fellow patrolman are standing over the lake, Hopper has a radio on his belt. The radio is a modern Motorola walkie talkie and at least a decade newer than it should be.
Chapter Two: The Weirdo on Maple Street - S1-E2
Factual error: When Steve and Nancy are making out, the intro to "A Hazy Shade of Winter" by The Bangles plays. While the original version of the song was released by folk-pop duo Simon and Garfunkel was released in 1968, the version heard here was released in 1986, 3 years after the scene takes place. (00:52:30 - 00:55:40)
Chapter Eight: The Battle of Starcourt - S3-E8
Factual error: The value of Planck's constant used in the show, 6.62607004 is the value that was measured in 2014. The value that was in use in 1985 was 6.626176. The value was updated again in 2018, to 6.62607015.
Chapter One: The Vanishing of Will Byers - S1-E1
Continuity mistake: When Will is being chased by the monster and runs into his garage, he pulls down his .22 rifle hanging on a wall rack. After he loads a few rounds aiming it at the door, the monster appears behind him. After Will and the monster disappear, the scene shows his rifle is back on the wall rack in its original spot. Did Will or the monster place it back on the wall rack while Will was being abducted? (00:07:25 - 00:08:10)
Chapter Eight: The Mind Flayer - S2-E8
Factual error: When El arrives, Hopper rifle has a picatinny rail, inaccurate for the time period.
Chapter Eight: The Upside Down - S1-E8
Factual error: When Nancy shoots the creature the second time, she fires at least 8 shots from a 6-shot revolver without reloading. And that's assuming she reloaded after firing 3 shots at the creature the first time, even though the situation made it seem unlikely. (00:20:30)
Chapter One: Suzie, Do You Copy? - S3-E1
Factual error: When Dustin's toy collection "comes to life" (thanks to Eleven), one of the robots is the Transformer Ultra Magnus. Though it appears to be modified with a motorized engine that the actual toy didn't have, that's not the mistake, as there no reason Dustin couldn't have modified it. The error is that the season is set in July 1985, but Ultra Magnus wasn't released in the U.S. until 1986. (Yes, the toy was available as a Diaclone in Japan, but in a different color scheme. Dustin's has the coloring of the U.S. version, and even if he somehow ended up with the Diaclone version, it's highly unlikely he would have repainted a Japanese toy to resemble a Transformer he wouldn't know about the existence of yet, as the 'Transformers' animated movie wasn't released until August 1986).
Factual error: During the police pursuit in Pittsburgh, the officers are wearing shoulder speaker/microphone handsets. The models are the Motorola Saber radio, which wasn't introduced until 1989, while the season takes place in 1984.
Chapter Nine: The Gate - S2-E9
Factual error: The military convoy has Desert Tan HMMWVs (Humvees). The Army didn't take delivery of the first ones until 1985 and they certainly were not painted Desert Tan until 1991 in the Gulf War.
Chapter One: The Vanishing of Will Byers - S1-E1
Factual error: The boys need Will to roll a 13 to hit the Demogorgon with the fireball in the DnD game. Fireball is an automatic hit. Players roll for damage only. They mention the 13 needed to hit in the final episode as well.
Chapter Five: The Flea and the Acrobat - S1-E5
Factual error: The bus that appears in the scene is a Blue Bird TC2000 dating from 1998 to 2003, long after the setting of the series. (00:38:15)
Chapter Eight: The Upside Down - S1-E8
Factual error: This error occurs multiple times during the Series but most after 11 and the demogorgon disappear from the class room a modern periodic table is shown. There's at least a 1/2 dozen elements on it that weren't discovered until the 2000's.
Chapter Eight: The Mind Flayer - S2-E8
Factual error: Joyce asks Will if he remembers when he was 8 and she bought him that giant box of crayons for his birthday - the 120 pack. Will is 13 in the show, so when he was 8, it was 1979. There were only 78 colors available in 1979 and the 120 crayons box was not available until 1998, almost 20 years later.
Chapter Seven: The Massacre at Hawkins Lab - S4-E7
Continuity mistake: Eddie is still wearing a denim vest he took off his body and threw at Steve a few seconds earlier. When the camera cuts away and back, the vest is gone again. (00:15:19)
Chapter Seven: The Bathtub - S1-E7
Factual error: When there is a pan closeup shot of the walkie-talkie the boys are going to finally talk to with the sheriff, there is a book called Great American Ghost Stories by Hans Holzer on the shelf to the left. That book was published in 1990, not in 1983, the year of the episode. (00:18:30)
Chapter Two: The Mall Rats - S3-E2
Continuity mistake: Steve throws his empty banana peel on the table in the back of the ice cream store, then is shown seconds later still holding the empty peel.
Chapter Five: The Flayed - S3-E5
Factual error: When Hopper steals the yellow convertible at the gas station mini mart, the gas pumps have vapor recovery boots on the nozzles. Those weren't in use for another half decade.
Chapter Five: The Flayed - S3-E5
Continuity mistake: When Hopper is taking Todd's car at the gas station he hands Todd a Slim Jim he was eating, then they pan away from them to show Joyce Byers and Hop talking. When the scene widens Hop has the Slim Jim back in his hand and hands it to Todd again. (00:24:25)
Chapter Seven: The Bathtub - S1-E7
Factual error: High school basket ball courts didn't have a three point line until the 1987-88 season - not in 1983.
Answer: The body was fake, made by the scientists at Hawkins Lab in an attempt to cover up his disappearance and the existence of the Upside Down.