In The X-Files, the Cigarette Smoking Man (played by William B. Davis) only smokes Morley cigarettes. Rarely seen without a cigarette in his hand, the CSM was originally intended to be a non-speaking character always lurking in the shadows, but he was eventually given dialogue and became the show's primary antagonist. In "Two Fathers" (Episode #126), his name was finally revealed to be C.G.B. Spender, and in several episodes it is strongly suggested that he is Fox Mulder's biological father.

Fox Mulder's middle name is William. Coincidentally, David Duchovny's middle name is William too.

In "Existence", the last X-Files episode of season eight, Alex Krycek (Nicholas Lea) is shot between the eyes and killed by FBI Assistant Director Walter Skinner (Mitch Pileggi). Krycek had been a thorn in Mulder and Scully's side since his first appearance in the series in season two when he was temporarily assigned by the FBI to work with Mulder. Of course, as it turned out, he was actually working with the Cigarette Smoking Man. Krycek played a key role in several tragedies that affected Mulder and Scully including the murders of Mulder's father and Scully's sister.

John Fitzgerald Byers (Bruce Harwood), Melvin Frohike (Tom Braidwood), and Richard "Ringo" Langly (Dean Haglund) are The Lone Gunmen on The X-Files. A trio of computer-hacking conspiracy geeks who publish an underground newspaper, Byers, Frohike & Langly often come to the rescue when Mulder and Scully have nowhere else to turn. The Lone Gunmen starred briefly in their own television series, a light-hearted spin-off of The X-Files, which first aired in March of 2001 and was cancelled in June of that same year. In "Jump the Shark", one of the final episodes of the X-Files (Episode #197 to be exact), The Lone Gunmen die trying to save the world from a deadly virus.

In "Arcadia" (Episode #132), when Mulder and Scully go undercover to find out why members of a California home owners association keep dying mysteriously, they take a page from The Dick Van Dyke Show (1961-1966) and use the aliases Rob and Laura Petrie -- the characters played by Dick Van Dyke and Mary Tyler Moore in the classic sitcom. Fortunately, none of the neighbors catch on -- apparently, they've never seen the show.

Throughout the course of The X-Files, Mulder has several informants who slip him information from within the conspiracy machine. His primary informants are Deep Throat, X, and Marita Covarrubias.

Scully's family, apparently, has a thing for Moby Dick. Her father called her "Starbuck", she called him "Captain Ahab", and her dog is named "Queequeg".

Mulder's favorite snack is raw sunflower seeds. In "Aubrey" (Episode #36), he reveals to Scully that his father used to eat them as well and suggests that his taste for sunflower seeds may be some sort of genetic memory. In "Anasazi" (Episode #49), Mulder asks for seeds while delirious with a fever.

In seasons 8 and 9 of The X-Files, John Doggett (Robert Patrick) and Monica Reyes (Annabeth Gish) replaced Mulder and Scully as primary investigators on the X-Files. Series creator Chris Carter believed that the series could continue for another ten years with new leads, but much of the show's fan-base was built around the relationship between the original characters, and the show was cancelled after its ninth season. Both Mulder and Scully made sporadic appearances throughout the final two seasons, and both returned for the final episodes.

In 1997, Gillian Anderson won an Emmy for Outstanding Lead Actress in a Drama Series. She was nominated again in 1998, along with David Duchovny, but neither won. However, The X-Files did win several other Emmys during its nine-year run, including Outstanding Individual Achievement in Writing for a Drama Series (1996), Outstanding Guest Actor in a Drama Series (1996), Outstanding Art Direction for a Series (1997 & 1998), Outstanding Special Effects for a Series (2000), and Outstanding Music Composition for a Series (2002). The X-Files also won a number of other awards including Golden Globes for Best Drama Series in 1995, 1997 & 1998.