Steve Perry, former lead vocalist for Journey, has said that the Stranger Things season 4 remix of Journey's 1980s smash hit Separate Ways (Worlds Apart) was done pretty much the way he originally wanted it done in the 1980s, but lacked the technology. Perry was so impressed that he even helped with the development of the remix.
Costume Designer Malgosia Turzanska was searching for a vintage army belt for Lucas in season 1. At an antique store in Utah she found one locked in a cabinet. Upon retrieving the belt she discovered on the back side written in Sharpie: "Lucas", the name of the original owner.
Max's theme song in season 4 is "Running up that Hill" by Kate Bush. The frequent use of the song led to it going to #1 on the US iTunes chart in the first week of the season's release. In 1985, the song did not go higher than #30 on the US Billboard chart.
In April 2018, filmmaker Charlie Kessler filed a lawsuit against the Duffer brothers, claiming that they stole his idea behind his short film Montauk, which featured a similar premise of a missing boy, a nearby military base doing otherworldy experiments, and a monster from another dimension. he pitched his film to the Duffer brothers and later gave them "the script, ideas, story and film" for a larger film idea which he called The Montauk Project. Kessler contended that the Duffer brothers used his ideas to devise the premise for Stranger Things and sought a third of the income that they had made from the series. The Duffer brothers' lawyer stated that they never saw Kessler's film nor spoke to him regarding it, and that Kessler had no input into their concepts for Stranger Things. The judge denied summary judgment for the Duffer brothers in April 2019, allowing Kessler's suit to proceed to trial. Just before the trial was due to start in May 2019, Kessler withdrew his lawsuit after hearing the depositions and seeing documents from as early as 2010 which showed him that the Duffers had independently come up with the concept of Stranger Things.