Alyson Hannigan

Into the limo go the stars of CBS’ sitcom “How I Met Your Mother.” Out of the limo they go. In the limo, out, in ... well, you get the picture. For this New Year’s Eve episode, Josh Radnor, Alyson Hannigan, Jason Segel, Neil Patrick Harris and Cobie Smulders will enter and exit this stationary limousine 16 times.

If it were shot like a regular sitcom, there would be a couple of takes of a scene like this, shot before a live audience in one night of taping. But for this episode - shot over three days - there is a partial limo on a sound stage, the actors and the crew but no audience. “How I Met Your Mother” is a one-of-a-kind hybrid that combines the lively effect of multi-camera coverage with the editing and cutaways of a single-camera show (think “Friends” mixed with “Scrubs”). That laughter you hear when the show airs comes from a post-taping screening with an audience.

There’s a method to this madness, explained series co-creator Craig Thomas.

“It’s harder to launch a sitcom these days. People are a little bored with the purely traditional form of it, but were huge fans of ‘Cheers’ and ‘Seinfeld.’ If you could do that sitcom but just update it a little bit and have it be a little quicker with a different narrative storytelling device, it would feel familiar enough but exciting enough that people might want to watch it.”

Getting people to tune in has not been a problem. Sandwiched in a cushy spot between “King of Queens” and “Two and a Half Men” on Mondays, “How I Met Your Mother” attracts a total 10.2 million viewers and is No. 1 in its 8:30 p.m. time slot among all of the key demographics. That means even the young - 4.7 million 18- to 49-year-olds - are tuning in to CBS, the network known for the most mature audiences. The show is more expensive to produce than typical sitcoms, but not significantly so, according to the network, with the cost of doing more scenes offset somewhat by the fact that it’s not shot in front of a live audience.

The problem on this recent afternoon is the limo. The writers figured it would be the simplest episode they have produced.

Wrong.

“You can only fit certain cameras in certain places, so you keep having to move around to get all the coverage,” Bays explained during filming on the 20th Century Fox lot. “Our idea of a nice, simple episode set in the limo has turned into quite an opus.”

Inspired by the friendship and love lives of its two 30-year-old creators, the show is a romantic comedy told from the point of view of a fiftysomething father (voiced by Bob Saget) in 2030 who is telling his teenage children the story of how he met the woman he married. The tale begins in 2005 and goes through the ups and downs of dating for 27-year-old Ted and his friendships with Marshall and Lily (Segel and Hannigan), his college buddies who get engaged in the pilot, and their eccentric and woman-loving friend, Barney (Harris). Smulders plays Robin, the woman Ted falls for in the pilot but who becomes a good friend instead of The One.

“It’s a slight departure from the more traditional family comedies we have on the air,” said Nina Tassler, CBS president of entertainment. “For a lack of a better description, the show has a contemporized nostalgia. If you were living in their world present day, you could completely relate to those characters and say my friends are just like that. If you are perhaps a little older, you can recollect with tremendous fondness what those days were like.”

For Bays and Thomas, those days were not so long ago. The two friends moved to Los Angeles four years ago, after Thomas married his college sweetheart, and the two buddies left their first television gigs in New York writing for “Late Night With David Letterman.” Here they wrote for “Oliver Beene” and “American Dad” until last development season, when they penned their first pilot based on their days living in Manhattan.

Ted is modeled after Bays, who is single; Marshall takes after Thomas, who met his wife during his freshman year of college.

“The title was the first thing that existed,” Bays said. “There’s inherently a great story in it because everyone is curious about that. For me, applying it to my own life, it does raise a question: What is my story going to be? What is the story that I’m going to tell my kids, not just about who I marry but how am I going to get to that place that I end up?”

As a result, the show is sweet and screwball, with Ted, Marshall and Lily conveying its heart; and Barney and Robin delivering most of the gags.

Bays and Thomas began the casting process wanting Hannigan and Segel for Lily and Marshall. Thomas’ wife, Rebecca, a devout “Buffy the Vampire Slayer” fan, agreed to let her husband create a character like her if Hannigan, who played Willow on the series, got her part. Happily for them, Hannigan was searching furiously for a comedy.

“You can relate to everybody or knowing somebody just like that,” said Hannigan, 31. “These are people you want to hang out with.”