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 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.
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.