At the end, when Dean and Sam are walking away, Dean says: "Did she look familiar to you?" "No why?" "I don't know. Anyways you hungry?" "No" "Man, for some reason I could really go for some pea soup." Linda Blair played Regan in The Exorcist (1973) and her vomit resembled split pea soup (which was actually used in the film). Linda Blair played the detective in this episode.
This is the first episode where Dean does not refer to Sam as Sammy.
Guest star Linda Blair had been approached about appearing in an episode in Season 1. She turned it down as she had been actively trying to disassociate herself from the horror genre, even though she was a self-professed fan of the show. She was very touched, however, when showrunner Eric Kripke personally pitched this episode to her and so changed her mind.
This episode is set in Baltimore, the town where Edgar Allan Poe died. He was famous for such stories as "The Cask of Amontillado" where a victim is concealed inside a brick wall. This story was based on something Poe witnessed during his military service at one of the forts in the Boston Harbor.
When Dean finds the papers with "danashulps" typed over and over, he says, "All work and no play makes Jack a dull boy." That's what Jack Nicholson types repeatedly in the horror classic The Shining (1980).