The table and chairs in Mike's home are direct replicas to the kitchen table and chairs in Poltergeist (1982).
This is the first episode in which Mike has not appeared.
This episode takes place on March 26, 1986.
Steve, Nancy, Eddie, and Robin hiding under the rock from the bats in the Upside-Down is very similar to the four Hobbits hiding from the Nazgul under the tree trunk in The Fellowship of the Ring (hence the Mordor reference).
As of the end of May 2022, this is the highest-rated episode of the entire series so far.