Scully's father and the man Mulder thought was his father were both named William. Mulder's actual father, Cancer Man, was played by William B Davis. Scully and Mulder's son was also named William.

In 2001, The Lone Gunmen were given their own self-titled TV series, The Lone Gunmen.

The Lone Gunman is a reference to the Kennedy assassination, in which the Warren Commission reported that a lone gunman, Lee Harvey Oswald, killed President John F. Kennedy. Ironically, Bruce Harwood's character, John Byers, is named after Kennedy.

Whenever the Cigarette Smoking Man smokes on the show, the actor is smoking herbal cigarettes.

There was no character or characters who appeared in all 201 episodes of The X Files.

Series creator Chris Carter changed the name of William B. Davis' character from "Cancer Man" to "Cigarette Smoking Man" about halfway through the series so tobacco companies wouldn't be offended. However, the character was still referred to by both names throughout the series.

Two numbers that appear frequently during the series are 1013 and 1121. October 13 is series creator Chris Carter's birthday, and November 21 is his wife's birthday.

The "I Want To Believe" poster in Mulder's office was a prop created exclusively for the show and wasn't intended to be made commercially available. However, popular demand caused Fox to release the poster for sale.

William B Davis (Cancer Man) spoke his first line in this episode.

The scar David Duchovny (Mulder) got on his left hand while shooting "Fire" can be seen in the bar scene after the sheriff takes the boy away.

When Mulder and Scully arrive at the government building with the fake IDs, Mulder's ID says he's Tom Braidwood. Tom Braidwood played Melvin Frohike in this episode and many others.

This episode originally included the following line of dialogue towards the end; Scully: Never let it be said that you wouldn't walk through fire for a woman, Mulder. Mulder: And never let it be said that I wouldn't do it for you again, Scully.

David Duchovny (Mulder) got burned while shooting a scene. The scar can be seen when he is at the party shortly before Phoebe arrives and asks if they can dance.

When Mulder and Scully are in the car park, and Howard Graves's car parking space is being renamed, the name being painted on is Tom Braidwood - who is the actor who plays Frohike and is also an Assistant Director of the series.

When Mulder and Scully are in the library, if you look at the newspaper report, above the story of Howard Graves suicide there is an article about a killer who extracts his victims livers and escapes from impossible locations. A reference to Eugene Tooms.

Doug Hutchinson is one of the two actors that played the character of Tooms, a liver eating mutant, in the episodes "Squeeze" and "Tooms." Hutchinson is actually a vegetarian, or was at the time. After filming "Tooms" he sent the liver of an animal to Chris Carter as a thank you for the opportunity to play a character on "X-Files."

The shot of Tooms going down the chimney to reach his fourth victim was not done by any visual effects. A contortionist named Pepper actually squeezed inside, and then the sounds of bones cracking and snapping were added later. Confirmed by co-executive producer Robert Goodwin.

The original script for this episode called for Mulder and Scully to howl at the moon at one point.

In the scene on the plane, the man who is sitting behind Scully is David Duchovny's father.

Chris Carter makes an uncredited appearance in this episode as an F.B.I. agent who asks Scully if she was assigned to debunk Mulder's work.