When Mulder and Scully arrive at the hospital the crawl at the bottom of the screen reads "Hartwell Psychiatric Hospital", but on their second trip to the hospital you get a close look at their visitor badges that read "Hartford Psychiatric Hospital".
In the last scene, where it counts down to the year 2000, you can see a sliver of the clock in one scene and it reads 51, 52 seconds. In the next shot, a close-up of the screen, the seconds are at 43.
The local cops think they are dealing with a dead man come back to life because Mulder said they found his fingerprints on the lid of the coffin and also a hand print on the back of the tombstone. However it would be pretty much impossible to get fingerprints off of a stone like that, the surface is way too porous for that.
The story is set at year's end in a country in the northern hemisphere yet all visible deciduous trees are still in full, green leaf.
In the opening when Mulder is in the grave, his hair part is on his right side. Later it switches to his left which it usually always is.
Mulder refers to the Book of Revelation as Revelations. Frank Black correctly refers to it as the Book as Revelation.