(Image credit: 20th Century Fox Television)

Sci-fi spin-offs can be a mixed bag. "Star Trek: The Next Generation" and "Stargate SG-1" were so successful that they spawned numerous follow-ups of their own, but efforts to expand the respective universes of "Babylon 5" ("Crusade") and "Battlestar Galactica" ("Caprica") proved rather less successful. Both were cancelled after a single run of episodes."The X-Files" spin-off "The Lone Gunmen" — whose final instalment debuted 25 years ago — belongs in that same one-season wonder category, but was rather better than its premature axing might suggest…Like "Cheers"' spawn "Frasier", "The Lone Gunmen" shifted the tone of the source material; it was lighter and more overtly played for laughs than "The X-Files", and it focused on characters who'd started out as supporting players.

(Image credit: 20th Century Fox)Conspiracy theorists/investigators John Fitzgerald Byers (Bruce Harwood), Melvin Frohike (Tom Braidwood, who also worked as an assistant director on the sci-fi smash's early seasons), and Richard "Ringo" Langly billed themselves, oxymoronically, as the Lone Gunmen.The brainchildren of X-Files legends Glen Morgan and James Wong (who'd later go on to make "Space: Above and Beyond"), the fan-favorite trio had been helping out Fox Mulder's investigations into the unexplained since season 1 episode "E.B.E.". Their presence had subsequently grown throughout the original show's run, and they'd even been granted an origin story in season 5 episode "Unusual Suspects".