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.
Factual error: When Mulder is walking out of the cabin in Spender's uniform, the soldiers try to stop him. This is impossible since he is an officer (a lieutenant judging from the shoulder-straps) and they are privates, so they cannot give him orders. The only thing they can do in this situation is to salute him.
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.
Factual error: In the opening sequence, we see a nuclear attack submarine beneath the ice in the Arctic Ocean. When the captain orders the ship to surface, one of the crewmen mutters, "Surface to what? We're under 32 feet of glacial ice!" Except that they're not under "glacial ice," they're under Arctic sea ice, which ranges from about 6 feet thick in the summer to about 15 feet thick in the winter.
Add timeCharles Austin Miller
Other mistake: In order to leave such bloody footprints, CSM must have stepped into the puddle of blood. It is impossible because the guy shot by CSM could not bleed so much blood in such short time, not mentioning that CSM must have intentionally stepped into it.