Twin Peaks connection: Richard Beymer plays a prominent role in this episode. Six years earlier, he played Ben Horne in Twin Peaks, which also featured David Duchovny in several episodes.
Episode Title: Sanguinarium
This is Latin for "Place of Blood". 'Sanguinary' means carnage, bloodthirsty or consisting of blood. Finally, 'Sanguinaria' means "Bloodroot".
Nurse Waite's name is most likely a reference to the 19th Century Occultist Arthur Edward Waite, whose name is still on Rider-Waite tarot decks.
The book that Mulder reads and learns that witches can make people vomit needles is the Encyclopedia Of Witchcraft & Demonology by Russell H. Robbins
Mulder says that belladonna is only found in one drug in the PDA (Physicians Desk Reference) but even 1996 there were more than that. Many Eye Doctors use it to dilate patient's pupils, amongst other things.
When Mulder and Scully are discussing the nurse's ingestion and subsequent vomiting of pins. Scully mentions pica which is a condition that makes people eat non-nutritious and non-edible things, such as rocks, glass, metal etc. Mulder then goes on to describe allotriophagy, which he suggests is a condition, possibly even a spell, that causes people to vomit things they never ingested in the first place. This is completely untrue. Allotriophagy is similar to pica in that it is defined as a depraved appetite or desire for improper food.
Mulder: Looks like she took a pretty good shot at you.
Dr. Franklyn: Yes. Apparently.
Mulder: Nothing that a little plastic surgery won't fix up though, huh?
Scully: What could she have been doing in here?
Mulder: Probably not tax returns.
In the operating room, Dr Lloyd is violently stabbing liposuction tool into unconscious patient, who at this point we see has lines drawn on his balding head. Fat being sucked through tube turns bright red.
Nurse Waite: Doctor Lloyd!!
Dr. Lloyd: (pulling down his mask) I think this patient is finished.
Scully: So this man committed these murders in order to make himself beautiful?
Mulder: Everybody wants to be beautiful, Scully.
Scully: Well, he started taking the drug 5 years ago and he went through . . . ooh, he took a lot of it. 19 100-tablet refills.
Mulder: (checking out a passing nurse) Wow.
Scully: (Thinking he's commenting at pill numbers) Yeah.
Dr. Theresa Shannon was named after the actress Shannon Tweed.
The words written in blood on Dr. Franklin's mirror are "vanitas vanitatum" or "vanity of the vanities".
The producers of The X-Files got an enormous amount of angry letters and emails from supporters of Wicca and ritual magic in response to this episode.