Visible crew/equipment: When Mulder and Scully are talking to the owner of the trailer park and he is berating Mulder, you can see the edge of the lens in the upper left corner of one shot. This is because the lens used was of a wide angle almost fish-eye type and the edge of the lens itself can occasionally creep into the frame on most cameras.
Continuity mistake: When we watch Scully typing from behind, the text she types is ahead of the text we saw at a distance in the previous shot. (00:15:15)
Visible crew/equipment: Near The Beginning, Mulder, Scully, and another man are walking through a graveyard. The camera is following them to the right passing head stones. The crew can be seen reflected in a black shiny head stone as the camera passes.
Red Museum - S2-E10
Continuity mistake: Scully is walking down the steps as Mulder and the sheriff are talking about the boy. In the wide shot she is halfway down. In the closeup she comes up from behind Mulder.
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.
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. (00:15:10)
Visible crew/equipment: When the Senator opens his car doors, a filming crew member in blue jeans is reflected in the door. (00:32:25)
Continuity mistake: When Skinner enters the embassy garage, the rear left window of his car is closed, but after the shot of the Tunisian diplomat the window suddenly becomes open. (00:21:30)
Continuity mistake: When the rain starts to fall, Daryl opens the window and reaches out his left hand. However, in the next shot facing the windscreen he holds the steering wheel with both his hands. (00:03:05)
Factual error: At The Beginning of the "Musings of a Cigarette-Smoking Man" episode Frohike says that the CSM appears when Trotsky was assassinated, i.e. 20 August 1940, but he does not claim that this is an exact date of birth. However, he further says that during the Nazi-Soviet Pact (1939-41) the CSM's father "kept NKVD informed on American plans to enter World War II" and for this reason he was executed before the CSM learned to walk. This means that his father could not have been executed earlier than in 1941. Assuming that babies learn to walk between a few months and 2 years, the CSM could not have been born earlier than in 1939. It means that in 1953 he should have been a young teenager, and not an adult man, as he is presented. (00:03:45)
Die Hand die Verletzt - S2-E14
Continuity mistake: Having finished his conversation with Scully by the tree stump, Mulder walks away. However, in the next shot he again starts to walk away from Scully and from closer than before. (00:07:30)
Other mistake: When Morris Fletcher walks into the bar, in the first mirror reflection Mulder and Fletcher are walking together (Mulder followed by Fletcher) for a short but noticeable moment. (00:16:50)
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)
Continuity mistake: When the car drives down the hill, the front and rear left window of the car is open, but in the shot from the inside of the car after it is stopped, there is Crump's blood on the closed rear left window. (00:40:05)
Revealing mistake: When Scully grabs Mulder's hand, his watch shows 11:25 AM, but when the agents enter the house, the scene's stamp reads "Phoenix, Arizona, 4:58 PM." (00:17:55)
Visible crew/equipment: Mulder talks to the man from NICAP on the other side of the fence. When the shot is looking at the man, film lights are visible reflected in his glasses. Since he is looking at Mulder, there should be lights on Mulder's side, but there are none.
Visible crew/equipment: Mulder is talking to the computer programmer in the prison. The shot starts on the bars and pulls back. A significant shadow caused by the camera is visible on the right side of the frame.
Audio problem: The man changing the flat tire in The Beginning of the episode drops his flashlight. He says "dang it" but his mouth doesn't move.
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