Interviews with "Firefly" staffers often include the question of "What story ideas were never produced?" As such, we know they were kicking around episodes about Kaylee having to go undercover as a Companion, and the Alliance accidentally producing a herd of mutant zombie cattle (yes, for real), but we'll probably never see those stories.
Like a lot of "Firefly" fans, I have mixed feelings about "Serenity," the 2005 movie that continued the saga. It's a solid movie by every important metric (the 7.9 IMDB rating, compared to 9.2 for "Firefly," seems about right). But by 2005, we had finally gotten to appreciate the 14 episodes in chronological order on DVD, and along came this film where -- as with the original haphazard airing of the series -- we felt like we were missing something.
Even in comparison to "Buffy" and "Angel" -- which had already built up complex mythologies by the fall of 2002 -- "Firefly" arrived as Joss Whedon's most completely detailed and believable fictional universe. He imagined a 26th century where corporations and government are one and the same, American-looking people swear in Chinese (and have Asian-sounding last names, in the case of the Tam siblings, or dress in Asian fashions, as with Inara), and where prostitution is legal and respected -- so long as the government can regulate it, of course.