New this week Revealing mistake: The answering machine at the end appears to not be plugged into any phone line. The shot shows the phone jacks on the right side of the machine are empty. In order for an answering machine to work at least one of those ports would need to be hooked to the phone.
New this month Plot hole: It is virtually impossible that such a conspiracy-experienced, cautious, and wise person as the Second Elder would be so naive and careless to just let the "Dr. Openshaw" faceless alien to his house, knowing from the CSM that Dr. Openshaw had died that evening.
Visible crew/equipment: I don't know if this is visible in all formats, but on the newest UK release on DVD, watching in widescreen, it's amazingly obvious. When Mulder recovers from the vampire attack, he gets up from the floor and breaks up a chair to make a stake. There is a shot of his feet as he smashes the legs off and bends to pick up a piece. In the bottom left hand corner of the screen, you can see a crew member's hand carefully and quickly placing a piece of wood on top of the pile for Mulder to pick up.
Visible crew/equipment: A mic boom operator is visible on the left hand side of the screen wearing a white t-shirt, beige shorts, and sneakers. He's carrying the boom mic and following Mulder and Scully. You can see him when Mulder and Scully arrive at the "Church of God with Signs and Wonders" for the first time...when Mulder delivers the line "That's funny, I knew a couple Catholic schoolgirls who were experts at it."
Revealing mistake: While the computer is being infected with the virus, Peterson turns away from the screen to face Scully. Two seconds later, after the shot of Scully, the same shot is shown again but in reverse so that Peterson turns back to the screen. It's more obvious if you look at the weird way his eyes blink in the reversed shot.
Continuity mistake: When Mulder experiences his near-death trance state his body is lying, apparently lifeless, in a star spangled sky. As the camera tracks in on him the toes on his right foot twitch, just after Deep Throat begins to speak. The foliage covering his chest also changes position between shots. In the wide shot he is covered up to the armpits. But the first close up shows his chest is exposed. Then in later close ups it is covered again.