PHOTO: Interfoto USA/Sipa

The mainstream world may have missed writer/director Joss Whedon’s sci-fi TV series, “Firefly,” and the movie it spawned, Serenity. But for a rising generation, he’s the new lord of the geeks.

Whedon outdoes his predecessors by truly living and preaching the underdog gospel. In addition to the “Firefly” mythology, his cult hits—TV shows “Buffy the Vampire Slayer” and “Angel”—still earn him raves. “His characters have significant flaws, but they can overcome and surpass those flaws through force of will,” says über-fan Scott O. Moore, “Fans love to believe that about themselves.”

Now, in this burgeoning You Decade of Hollywood, Whedon’s acolytes are paying the ultimate tribute by re-engineering their hero’s defeated shows into new online series. “It means they care about the work, that I’m asking the right questions,” Whedon says. “I found a way to their collective hearts.”

Spoken like a gentleman, one might say, given the sensitivity artists normally show when others make use of their work. Lawyers have threatened to sue girls for singing songs around a campfire without first paying royalties to the copyright holders. Whedon, however, takes a longer view of fans who base their fiction on his own. “I’m sure there’s bad work out there,” he says. “But ultimately, if someone’s taking it to their heart, that’s why I’m here. I make a living; I made sure that I do. All they’re doing is spreading the word. It would be both stupid and selfish to try to quash it.”

This isn’t the usual fan fiction. Moore has dumped tens of thousands of dollars into his online Angel parody, “Cherub.” A 17-year-old high school girl makes “Forgotten Memories,” a series of trailers for imagined episodes of “Buffy the Vampire Slayer”; it’s a hot download on YouTube. “Into the Black” is a coming Web drama, complete with professional special effects, set in the Firefly universe.

“The fandom is rabid,” says “Into the Black” cocreator, Damien Spracklin, “because Joss’s stuff always gets canceled.” Next month, Whedon’s troops—some of whom call themselves Browncoats, after the independent army in “Firefly”—are convening for their first-ever convention.

For Whedon, 43, TV geekdom is in his blood. His dad wrote for such shows as “Benson,” “Alice,” and “The Golden Girls,” and his grandfather was a writer on the “Andy Griffith” and “Donna Reed” shows. However, Whedon’s innate appreciation for the craft of screenwriting has a decidedly high-tech twist. “I was a lonely sci-fi fan boy growing up,” he says. “I would write science fiction and draw and mostly read voraciously and see movies and hang out with my best friend. We were a fan base of two.”

Unlike his fans, Whedon didn’t attend “Star Trek” conventions, but he got into the fold soon enough. After studying at Wesleyan University, in Middletown, Conn., he made the rounds in Hollywood, sharpening his nerd king chops on standbys including Alien: Resurrection, Titan A.E., and X-Men. His big break came in 1997, with “Buffy,” a TV series that chronicled the adventures of a young woman fighting an underworld of vampires. The show’s strong female characters and campy sense of fun made it a cult hit and spawned the spin-off, “Angel.” It also ensconced Whedon in the new pantheon of Hollywood heroes.

“All you get with Star Wars is the Empire versus the Alliance—black versus white,” says Moore. “With Joss, you get so many shades: the vampire down the street is evil, but he’s also sexy; slaying demons is important, except when the demons are on your side; the Reavers are horrifying mostly because they’re just inevitable versions of us. Joss always has his eye on how the situation can instantly change, suddenly putting all the audience’s preconceptions up for grabs. That feels fundamentally realistic, even if the trappings are fantasy or science fiction.”

Eric Tong, cocreator of “Into the Black,” agrees. “I think Joss attracts such passionate fans because he is a fan himself,” he says, “He knows what people love and want to see. One thing common to all Whedon TV shows (and to Serenity) is that they are a mix of all genres. Each show is part comedy, drama, horror, sci-fi, western, action, etc. Not only do his shows appeal to those kinds of audiences, but he and his team combine all those elements well.”

Like the computer-game modification community—also known as mod makers—Whedon’s fans became active participants in extending his mythology. Any kid with a computer and an Internet connection can pick up where he left off and create something new. Such interaction is inherently changing the rules of the industry. Fans don’t have to sit back and passively watch a show run its course. They can just fire up a digital video camera, shoot a sequel, upload it to the viral video hub, YouTube, and keep the flame alive.

Whedon isn’t alone. New serial dramas—such as “Heroes,” “Lost,” and “Battlestar Galactica”—are breeding new communities of passionate followers online. Some of those fans are hosting online radio shows, creating graphic novels, and screen art.

Chalk the explosion of interest up to two converging trends: a richer, more complex variety of screenwriting and the boom of so-called Web 2.0 user-created content outlets, such as Second Life and MySpace.

The acolytes speak to the bold new power of fandom in the digital age, Whedon says, “The point of any great fiction is to make you want to live there. Now fans can live there with other people. This is something I encourage and nourish as much as humanly possible.”

He had good reason. When “Firefly” got canned, the Browncoats lobbied Universal Studios to put out Serenity, a “Firefly” movie. It’s a pattern that dates back a long way, to when fans of the original “Star Trek” television series, angered by its cancellation, lobbied for its continuation by another means—the movies.

Now, in addition to blogging on Whedonesque.com, a hub for all things Joss, Whedon’s giving followers the ultimate Mana: continuations of the “Buffy” and “Serenity” sagas in comic books. “There is no bigger Buffy geek than me,” he says.