In season 2, There are at least two different versions of Billy's blue Camaro used for filming as the vehicle will randomly switch from having power windows (as seen in S2:E2) to having manual crank style windows (as seen in S2:E5).
When Erica tells Dustin and Robin that she wants ice-creams for life, she takes a cherry with her left hand. The shot changes to her back, and now she is taking it with her right hand.
At the end of chapter 6 Mike and Dustin set their bikes down outside of Mikes house with Dustin's bike on the left and Mike's on the right. In the beginning of chapter 7 when they are leaving Mike's house to escape, Dustin's bike is now on the right and Mike's is on the left.
In season 2 Dustin has new front teeth. In season 3 they're gone again without explanation. S3E1 when the gang surprises Dustin in his house it's obvious.
During a number of episodes, people are seen 'interrupting' someone talking on a two way radio or CB - that is, one person is talking/transmitting, and another person transmits to interrupt them, and then the other person hears this interruption and stops transmitting. This was done a few times on the kid's CB radios, and on the radios used by the police. Those radios - the CB and the police radios of the era from the show - don't work like that. If you are transmitting, and someone else transmits, you will not hear them.
The US flag patches worn by the police officers are incorrect. On the patches, the field of stars has too many stripes to the right of it and not enough stripes underneath. On the actual flag, the field "sits" on the fourth white stripe from the top. On the patches, it "sits" on the red stripe below it, the fifth red stripe.
CORRECTION: It's a myth that it's a "Federal offence" to impersonate a member of law enforcement by wearing an actual uniform in a movie or TV show. (It is a state offense to impersonate a police officer.) Accurate uniforms are allowed, but most production companies either don't bother to get them right, or don't work with the local LE agency and get their permission, and thus come up with something close but not quite right.
CORRECTION: It's a myth that it's a "Federal offence" to impersonate a member of law enforcement by wearing an actual uniform in a movie or TV show. (It is a state offense to impersonate a police officer.) Accurate uniforms are allowed, but most production companies either don't bother to get them right, or don't work with the local LE agency and get their permission, and thus come up with something close but not quite right.
In scenes where the CB radios are used, No one uses a Handle, which was a staple of the radio's use. No one uses either "Copy" or "Break" to end conversation, which was important on CB. Plus, CB was an open system which meant anyone can listen in on your conversation, no one would ever give away their location (Or their "20") in any case.
Eleven is unfamiliar with the word "friend" until Mike tells her what it means. When she is being led to the Sensory Deprivation Chamber by Dr. Brenner, he tells her that all the scientists are "friends".
In reference to a previously listed goof, Lucas was referring to John Carpenter's "The Thing"(1982) being a remake of "The Thing from Another World"(1951) not the 2011 remake. Whether it stinks or not is irrelevant. Season 1 takes place in 1983 and season 3 takes place in 1985.
The third season poster (One summer can change everything) shows Eleven bleeding from the wrong nostril. Eleven bleeds from the left nostril, not from the right nostril.
The maple syrup bottles did not have flip-top caps in the 1980s.
When laboratory workers use hazard suits, there's clearly bright blue or white LEDs lighting up the face of the wearer. However, white LEDs were possible only since 1994 when Shuji Nakamura discovered high brightness blue LED, which emit white light when covered in phosphor coating.
When Mrs. Wheeler is putting on makeup and perfume, the song "Died In Your Arms" is playing in the background, this scene took place in 1985 but the song came out in 1986.
The teenage characters frequently use the phrase "chill" to mean hang around. In 1983, "chill" would have been used as a command to someone the speaker perceived to be overexcited about something. "Chill" didn't mean "hang out" until some point in the 1990s.
The back of the magazine that Murray is reading on the plane is for MMA, its 1986 and that term was not used until 1993.