Trivia: Spoilers. You can briefly see at one point that Margot's high school mascot is an anthropomorphic catfish. In internet slang, "catfishing" is when someone pretends to be someone else online in order to "lure in" others. This is a very subtle clue to the ending, in which it is revealed that the user "fish_n_chips" was a boy who was "catfishing" Margot online.
Trivia: Contemporary or modern-day altered version of the "BTK" (Bind, Torture, Kill) serial killer - Dennis Rader - who murdered at least ten women from 1974-1991 in the Wichita, Kansas area. Rader was arrested in 2005 and received ten life sentences, but the "Clovehitch Killer" was killed by his son and made to look like an accident or suicide.
Trivia: The name of the demon, "Valak" can be seen on the playground equipment where we first see sister Irene.
Trivia: Part of what made the Coen Brothers agree to make the film for Netflix was that the traditional studio system just isn't funding films like "The Ballad of Buster Scruggs" the way they used to. Studios are instead focusing much more on big-budget comic-book movies and reboots, or super low-budget ventures like horror films. The Coens found Netflix to be one of the only companies that seemed to understand the project and be willing to fund it. Although co-director Joel Coen did lament that he wishes the film had a traditional theatrical release, as he feels audiences respond to and respect movies in a different way on the big screen.
Trivia: The American and international versions of the film have different opening sequences. In the American version, Holmes and Watson meet in school. In the international version, Holmes (accidentally) saves Watson from committing suicide.
Trivia: Lewis' new friend, Rose Rita, is the main character in other books by John Bellairs, author of the original novel.
Trivia: The protagonist browses the archives of local newspapers to research more into the fire of May 3rd 2003. The news at the very top right of the front page, by the title "Town treasurer celebrates his re-election after disputed elections" features a mugshot of the director of the movie, Paul Feig. (01:20:25)