Continuity mistake: When Jeff is shown for the first time inside the car, we can see that Mulder's face is facing the windshield, but in previous and next shots he is turned toward his colleagues. (00:05:25)
Continuity mistake: When the craft is flying over Scully, Mulder, and Morris Fletcher, in the first shot Fletcher stands with his back turned to the agents, but in the next shot he is facing them. (00:03:10)
Visible crew/equipment: When Mulder is driving away from the gas station, crew members as well as some filming equipment can be seen reflected in the car's body. Mulder is in a pretty desolate area, so seeing people reflected in the car's body would in all likelihood be crew members and not random citizens. (00:28:30)
Revealing mistake: When Mulder - whilst trapped in the body of Morris Fletcher - is doing various poses in front of the mirror, several of his movements and the corresponding movements from the realized reflection of Morris Fletcher are slightly out of sync with each other.
Answer: As he stated many times throughout the series, Mulder needed Scully to be sober and skeptical. Whenever Scully's skepticism wavered and she started questioning her own rationality, Mulder would try to restore her sense of skepticism, because he needed her to be clear-thinking.
Charles Austin Miller