Answer: The Lone Gunmen

The Lone Gunmen were a trio of fictional characters that appeared in the X-Files universe both in all ten seasons of the broadcast television show as well as the X-Files comics. The three men, Byers, Frohike, and Langley, seen here left to right and portrayed by Bruce Harwood, Tom Braidwood, and Dean Haglund, respectively, were ardent conspiracy theorists and fans of Agent Fox Mulder’s tireless work in the pursuit of the truth about everything from the disappearance of his sister to the role of the government in conspiracies big and small.

Not only did the three actors make an appearance in every single season of the X-Files, typically in multiple episodes of each season, but they were the only characters in the X-Files franchise to end up in their own spin-off show. In 2001, the three conspiracy buffs got their own show which lasted one season, airing 13 episodes between March 4, 2001 and June 1, 2001. The show was well received by X-Files fans but didn’t have strong enough ratings to get a green light for a second season. The show ended on a cliffhanger which, thanks to Chris Carter’s creative control over both the X-Files and The Lone Gunmen, could be resolved in the ninth season of the X-Files so fans weren’t left hanging.

The most notable element of the spin-off show was the uncannily prescient pilot episode which focused on a U.S. government conspiracy to hijack an airliner and fly it into the World Trade Center to drum up populist support for a war. When real life conspiracy theorists proposed just such a conspiracy in light of the actual terrorist attacks six months after the show aired, you can be certain more than a few of them made reference to the plot of the pilot episode.