Since Cokely is hooked up to an oxygen tank he certainly shouldn't be smoking, as that could make the whole thing explode. It's surprising that no one even commented on this.
At 37:11, when Mulder gets out of the car. There is a visible reflection of the boom-mic and operator in the car door.
This one's a small continuity goof - in the scene where BJ wakes up to discover she's been slashed, first she sits up in bed and we see her in medium profile with the bedroom lights out - the room looks completely black. In the next shot, a closeup, as she discovers she has some foreign substance on her, it looks as if the lamp has already been turned on - the wall behind BJ is slightly lit and you can see that it is brown. In the next shot, back to the profile, the room has gone back to being pitch black, then BJ reaches over and switches on the lamp, at which point the wall looks brown again.
When Scully is looking over the file on Agent Chaney, the shot over her shoulder shows the page turned over but from Mulder's point of view it is not.
Agent Chaney's body was awfully close to the surface so surely it would have been discovered sooner, especially if the field had been cultivated or slashed in the last 50 years.
When BJ is digging the basement for the second body and Mulder and Scully run down the stairs, watch closely and you can see that Gillian trips on one of the stairs and David grabs her to steady her.
Mulder: Well, on a basic cellular level, we're the sum total of all our ancestors' biological matter. But what if more than biological traits get passed down from generation to generation? What if I like sunflower seeds because I'm genetically predisposed to liking them?
Scully: But children aren't born liking sunflower seeds. Environments shape them; behavior patterns are taught.
Mulder: There are countless stories of twins separated at birth who end up in the same occupation, marrying the same kind of people, each naming their child Waldo.
Mulder: Jung wrote about it when he talked about the collective unconscious. It's genetic memory, Scully.
Mulder: Well, I don't want to jump to any rash conclusions, but I'd say he's definitely our prime suspect.
Scully: But Mulder, the man we're talking about is 77 years old.
Mulder: George Foreman won the heavyweight crown at 45. Some people are late bloomers.
Mulder: Anyway, this still doesn't explain BJ's connection to all this.
Scully: What if it's cryptamnesia?
Mulder: You mean consciously forgotten information?
Scully: Mulder, I don't think BJ was in the woods that night because of engine failure.
Mulder: What are you talking about?
Scully: Well, the Motel Black would have been the perfect meeting place -- away from town, away from his wife ...
Mulder: What do you mean?
Scully: It's obvious BJ and Tillman are having an affair.
Mulder: How do you know?
Scully: A woman senses these things.
Mulder: Listen to this, Scully. "One must wonder how these monsters are created." Chaney wrote this. "Did their home life mold them into creatures that must maim and kill, or are they demons from birth?"
Scully: Well, that's poetic but it doesn't help us much. What did he say about the 1942 homicides?
Mulder: Well, the press called the murderer "The Slash Killer." His three victims were all young women aged twenty-five to thirty. He disabled them with a blow to the head. He would carve the word "SISTER" on their chests and paint it on the wall with their blood.
Mulder: Have you ever, um, have you ever had any clairvoyant experiences? Premonitions, visions, precognitive dreams, things like that?
Tillman: What the hell kind of question is that?
Scully: What's your interest in this case?
Mulder: During their time, Chaney's and Ledbetter's ideas weren't very well received by their peers. Using psychology to solve a crime was something like, um ...
Scully: Believing in the paranormal?
Mulder: Exactly. There's another mystery.
Scully: Which is?
Mulder: Well, I'd like to know why this policewoman would suddenly drive her car into a field the size of Rhode Island and for no rhyme or reason dig up the bones of a man who's been missing for fifty years. I mean, unless there was a neon sign saying "Dig Here" --
Scully: I guess that's why we're going to Aubrey.
Mulder: Yes, and also I've always been intrigued by women named B.J.
Mulder: Well, that's a pretty extreme hunch.
Scully: I seem to recall you having some pretty extreme hunches.
Mulder: I never have!
The movie that Cokely is watching is the 1940 film His Girl Friday.
Terry O'Quinn´s appearance as Agent Darius Michaud in The X-Files movie confused some viewers who mistook him for his character Peter Watts from Millennium and who were, no doubt, unused to the concept that an actor may play several roles within one series/fictitious universe. O´Quinn reappears in season 9 as yet another character, aptly named Shadow Man.
Terry O'Quinn starred as Peter Watts in Chris Carter's Millennium and also as General Omar Santiago in Carter's short lived series Harsh Realm.
Mulder's fascination with women named BJ probably has something to do with David Duchovny's then girlfriend Perry Reeves playing a woman named BJ on Doogie Howser M.D..
Scully: I don't think Mendel had serial killers in mind when he developed his theory on genetics.
Mendel was an Austrian monk who is considered the father of genetics. He discovered, through a study of pea plants in 1856-1863, that there is a particulate inheritance of traits that follow certain rules. The meaning of this discovery was only fully comprehended at the turn of the 20th century.
Mulder: Jung wrote about it when he talked about the collective unconscious.
Jung was a Swiss psychiatrist who is considered the father of analytical psychology. Jung believed that one could understand the psyche through an extensive analysis of dreams, art, mythology, religion and philosophy.