When Scully calls for help after the first attack in their home, she says her badge number is XF072161. However, later on, when she pretends she has arrested Mulder in order to get into the Titanpointe building, she tells the young FBI agent that her badge number is XF071261. Both these numbers are completely different to her first badge number revealed in Teliko (1996) (JTT0331613), which, in turn, is also different to the one used in Christmas Carol (1997) (2317616).
The tombstones at the cemetery are incorrect for U.S. military ones. They should list the wars served in by the decedent as well as their highest medals earned.
One of the tombstones at the cemetery has a typo, reading "Airforce" instead of "Air Force".
Arlington National Cemetery is in Arlington, Virginia, not Washington, D.C.
When Mulder and Scully visit Arlington National Cemetery looking for the graves of the Lone Gunmen, they encounter Byers' grave first. His headstone displays his name as "John Fitgerald Byers" (sic). This is a misspelling of his middle name, as it is missing the letter "Z." The correct spelling is ""Fitzgerald," known to be the case because he was named in honor of 35th U.S. President, John Fitzgerald Kennedy.