William B. Davis' screen credit as the "Cigarette Smoking Man" usually appears at the beginning of whatever episode he's in. Since this would spoil the reveal at the end of this episode, his name appears in the closing credits as a special appearance instead.
There is no visible injury on Scully's left hand during the first hospital scene but she wears bandages in the next scenes.
Mulder: Krycek, you're a murderer, a liar, and a coward. Just because you stick a gun in my chest means I'm supposed to believe you're my friend?
Skinner: Over the past 5 years I've doubted you, only to be persuaded by the power of your belief in extraterrestrial phenomena. And I'm doubting you now not because of that belief but... because extraterrestrial belief is frankly the more plausible explanation.
Mulder: Then I suggest you put *that* into your report.
Krycek: You must be losing it, Mulder. I can beat you with one hand.
Mulder: Is that how you like to beat yourself?
(Krycek cocks the gun)
Mulder: If those were my last words, I can do better.
Krycek: Hear this, Agent Mulder... listen very carefully because what I'm telling you is deadly serious. There is a war raging, and unless you pull your head out of the sand, you and I and about five billion other people are going to go the way of the dinosaur. I'm talking planned invasion. The colonization of this planet by an extraterrestrial race.
Mulder: I thought you were serious.
Krycek: Kazakhstan, Skyland Mountain, the site in Pennsylvania. They're all alien lighthouses where the colonization will begin, but where now, a battle's being waged. A struggle for heaven and earth. Where there is one law: fight or die. And one rule: resist or serve.
Mulder: Serve who?
Krycek: No, not who. What.
Scully: What are you doing sitting here in the dark?
Scully: Thinkin' about what?
Mulder: Oh, the usual. Destiny. Fate. How to throw a curve ball...
The list of Skyland Mountain victims viewed by Scully in her hospital room is made up of the names of X-Files staffers.
The altered tagline for this episode "Resist or Serve" is used as the title for the X Files Playstation 2 game released in 2004.
Jack Finn, who played Cigarette Smoking Man's young messenger, is the son of Producer Joseph Patrick Finn.
Another altered tagline 'Resist Or Serve', spoken by Krycek: "A struggle for heaven and earth. Where there is one law: Fight or Die. And one rule: Resist or Serve".
Literary allusion: The Red and the Black
Possibly relates to Stendahl's novel Le Rouge et le Noir (The Red and the Black) which is filled with duplicity. The "hero" is a young cleric whose religious beliefs owe more to career advancement than any real faith. He tries to kill his lover during church service; she survives but he is still found guilty and guillotined for the crime. This episode is certainly filled with duplicity and there are plenty questions concerning faith and beliefs. Mulder also believes Scully was killed along with the other burned abductee victims before he finds out she has survived.