Alyson Hannigan

On a recent day here, the sunny New York City set on a sprawling studio lot was a crowded place.

Dozens of extras clad in running gear and drenched in fake sweat ran by cameras for take after take, as technicians, makeup folks and scores of staffers milled around. Given the number of people on hand and the scope of the production, it looked as though a feature film was being made.

This is the set of a sitcom? A supposedly "traditional" sitcom at that?

The sweaty runners were participating in the back-lot marathon for a February episode of "How I Met Your Mother." The CBS show about five friends in New York City, which manages to be both whip-smart and endearingly sweet, is part of CBS’ Monday lineup of mostly traditional, multicamera sitcoms. That term refers to shows that use up to four cameras at once to film a half-hour comedy in front of an audience on a soundstage.

Except we weren’t on a soundstage. And there was no audience. "HIMYM" does have a laugh track, but it’s inserted well after the show shoots for three solid days. Most sitcom tapings last three hours.

"It’s definitely ... a lot easier than a one-hour [show], but it’s a lot harder than a traditional sitcom," says Alyson Hannigan, one of the show’s leads. "People are like, `What do you mean, you need three days to shoot an episode?’"

A lot has been written about the supposed demise — and even the comeback — of the half-hour comedy on network television. Traditional sitcoms, we’re often told, are too stodgy and predictable and are just not cutting it anymore, while "single-camera" comedies such as "The Office, "My Name Is Earl" and "30 Rock" are all the rage.

But the line between "30 Rock" and "HIMYM" is not that distinct. Just as "Ugly Betty" isn’t quite a comedy and isn’t just a drama, "HIMYM" is something of a hybrid.

For one thing, some "single-camera" shows use more than one camera at a time. And though "HIMYM" does have a laugh track, the fact that the laughs (from a studio audience that watches a tape of the show) are put in after filming means the comedy is not "a slave to the audience" as executive producer Greg Malins says.

"You’re not writing to their reactions and writing to the lowest common denominator," Malins says. On other shows he has worked on, "any time you need to replace a joke and you just put the word `panty’ in there, the audience goes nuts. It’s hard to resist that."

"HIMYM’s" stories are told with more scope than many traditional sitcoms employ. A typical episode of "Friends" might have had a dozen scenes, maybe 18 at the most, Malins says. The "HIMYM" episode being shot last Wednesday had 53. The show’s pilot had 60 scenes.

"There’s no way we could shoot this amount of material in front of an audience," says co-creator Craig Thomas. "It would blur the line between `audience’ and `hostage situation.’"

"The terms single camera and multicamera are vestiges of another era of TV," says Carter Bays, the show’s other creator. "They’re pretty vague categories at this point. Every show is its own animal."

Despite the things that make it distinctive and different, "HIMYM" is still thought of by many as a traditional sitcom. And the people behind the show are conscious of the fact that if they were perceived as a single-camera show, "HIMYM" — which is a steady ratings performer with an avid fan base — might be more of a media darling, and could even become a breakout hit.

"If we were on NBC on Thursday, you’d realize quicker that we’re more like `Scrubs,’" Thomas says.

Though he’s a devoted fan of cult fare such as "Veronica Mars," Bays says, quite simply, "I want it to be the big hit."

And they’re trying to make that happen through traditional and new-media promotional tactics. "Dancing With the Stars" champ Emmitt Smith was on the lot that day, filming a scene for the episode that will air the day after the Super Bowl.

The creators also have their fingers crossed that "HIMYM" will turn up on iTunes soon. The show’s ladykiller, Barney, has a blog on CBS.com, and a MySpace page featuring a music video from another character, Robin, in all her former glory as teen-pop princess "Robin Sparkles," was a hit: Her video has been streamed more than 400,000 times since its debut.