Jason Carver convincing his crew that Eddie is part of a cult for the devil is a reference to the Satanic Panic that started in the 1980s in the United States.
Dustin mentions the villain of A Nightmare on Elm Street (1984), Freddy Krueger. The actor who portrays Freddy Krueger, Robert Englund, appears in Chapter Four: Dear Billy (2022) as Victor Creel.
When the kids are searching the old Creel house, Lucas jokingly suggests to Max that if they "hit these [piano keys] in the right combo, we might just open a door to [Vecna's] secret lair," referencing The Goonies, which came out in 1985 and co-starred Sean Astin, who also played Bob Newby in Season 2.
In contrast to the first season, Millie Bobby Brown's hair was not cut short for this one. Her "buzz cut" look in this season was actually the result of a complex wig and makeup procedure that took 30 minutes to apply before each day of filming.