Zed and Chas mention that Constantine's headquarters are larger on the inside and that its dimensions change. In the comics this place is known as the "House of Mystery." It made its comic debut in House of Mystery #1 in December 1951. It is known for being able to change its dimensions and location of its rooms, having a "mind" of its own, and for having both Constantine and Swamp Thing as caretakers.
The charmed playing card Constantine uses to fool the nurse shares many similarities with the psychic paper from Doctor Who (2005).
Papa Midnite is a comic book character who made his debut in Hellblazer #1 (January 1988). He is known for practicing voodoo magic and near immortality.
The backstory to this episode, about a Blues man who sells his soul for success and later disappeared, echoes the story of legendary blues guitarist Robert Johnson. Johnson is reputed to have sold his soul at a crossroad to become a genius guitarist, and died at the age of 27. Some say that Johnson was the first to be part of the 27 club/curse. 27 club/curse is famous people who all died at the age of 27 most of them musicians.
The exorcism Constantine uses on the Acetate begins the same as the exorcism commonly used by Sam and Dean Winchester on Supernatural