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.