Revealing mistake: When Bob and Joyce have lunch, Bob pops open a can of soda (which is period appropriate). The scene cuts to Joyce, then back to Bob. It is clear from how he is holding the can, and how he pretends to drink from it, that his newly opened soda is actually empty.
Stranger Things (2016)
1 revealing mistake in season 2 - chronological order
Starring: Winona Ryder, David Harbour, Millie Bobby Brown, Finn Wolfhard, Dacre Montgomery
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 Mall Rats - S3-E2
Trivia: The song Scott Clarke is listening to is not 'My Sharona, ' but actually 'My Bologna, ' by Weird Al Yankovic.
Chapter Four: The Body - S1-E4
Question: Where did the body of Will come from? And why was it stuffed full of cotton?
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.