Continuity mistake: Pusher loads the revolver with one bullet, leaving five chambers empty. When Mulder picks it up and points it at Pusher, the bullet can be seen in the cylinder, just to the right of the gun barrel. Later, when Mulder begins to slowly pull the trigger for the third time (aiming at Scully), we see the cylinder turn to Mulder's left. Problem is, with the bullet situated as it was when Mulder picked it up, the bullet would have moved to the barrel and been fired the first time he pulled the trigger, killing Pusher. Instead, it fires on the third pull.
Revealing mistake: In the opening sequence, a man who is hallucinating badly is apprehended by the police. They find a dead blonde woman in the trunk of the man's car. In a close-up of the dead woman, all the dried blood on her face is an added digital effect; however, the dried blood "drifts" around, seemingly out-of-sync with the video. Similar "drifting" digital effect problems are seen in other X-Files episodes.
Revealing mistake: As Dana Scully is examining the dead woman found in bed with Skinner, she observes a strange luminescent glow on the woman's nose and lips. It's apparent that this glow was added digitally; but the digital effect is "drifting" around the dead woman's face, seemingly out of sync with the video. Similar "drifting" digital effect problems are seen in other X-Files episodes.