Many of Egon Spengler's favourite snacks make a reappearance in the movie, such as Cheese-It crackers, Crunch, and the Twinkie.
The Revelation 6:12 prophecy written on the junk in front of the farmhouse is the same Bible verse Ray quotes in S.O.S. fantômes (1984). When Ray is seen again, he has the verse tattooed on his arm. The verse says: "I watched as he opened the sixth seal. There was a great earthquake. The sun turned black like sackcloth made of goat hair, the whole moon turned blood red."
Actual photos of Carrie Coon from her childhood and adolescence were used on the board that Egon used to track Callie's growth over the years.
Finn Wolfhard did not know he was auditioning for this movie. The audition sides were purposefully kept generic and vague as the movie was developed in secret.
Tracy Letts: playing the shopkeeper who tells Callie (Carrie Coon) more about the Dirt Farm. Letts is Coon's real-life husband.