Olive drab is the fashion color of the day, but the atmosphere in the jammed space, about the size of your typical suburban living room, in Building 795 on the huge Fox lot, is more toward fire-engine red.

Waves of laughter - it’s infectious - roll through the crowd of roughly 50, crammed on folding chairs around five actors facing one another across two tables, orchestrated by crackerjack comedy director Pam Fryman, who left Villanova 27 years ago and still calls home to her mom every day.

It’s the Monday "table read" for the season’s 17th episode of How I Met Your Mother, "Arrivederci Fiero," which airs tomorrow at 8 p.m. on CBS3. The script is getting life for the first time, under scrutiny of bosses and underlings from the show, the studio and the network.

Fryman, mother of twin 14-year-old girls, has been midwife at the birth of sitcom episodes like this hundreds of times on 40 series from Caroline in the City to King of Queens. James Burrows, who everybody knows is the best sitcom director in the business, has modestly called her the second-best.

The five stars of Mother, TV’s fifth-highest-rated comedy, in its second season, are a typical mix of 20s and early-30s sitcom actors. Neil Patrick Harris (Barney) starred 15 years ago as Doogie Howser. Even earlier, in the short-lived Free Spirit, Alyson Hannigan (Lily) had full-time work as a teenager opposite a nanny who was a witch. Later, she spent seven years starring as a witch herself in Buffy the Vampire Slayer.

Canadian Cobie Smulders (Robin) and Ohioan Josh Radnor (Ted) have never had regular sitcom roles before. On this day in late January, Radnor’s mom and dad are in from Columbus to hear him perform. They get a round of applause when introduced.

The actors seem to have made a fetish of dressing down, though it’s hard to tell if the tweed overcoat Jason Segel (Marshall) wears over his frayed jeans is from the thrift shop or cost $1,000 in a Melrose Avenue boutique. Hannigan sports an olive hat that looks like something Fidel Castro’s niece might wear. Radnor wears olive jeans.

They read the script out loud, together for the first time. They’re supposed to have familiarized themselves with it over the weekend, though Smulders comments later that Segel often seems "delighted at what he discovers" at each week’s table read.

The actor, whom TV fans might remember from two delightful but short-lived shows about students, NBC’s Freaks and Geeks and Fox’s Undeclared, mutters something about the importance of "fresh eyes."

It’s Hollywood. Everybody has his method.

Prepped or not, the actors breeze through the script at the table read, drawing chuckles, laughs and guffaws from the hangers-on. Sometimes, the critic in the room laughs, too. Sometimes, he wonders if the others aren’t just being polite to spare the writers’ feelings.

They’re not supposed to be. "We don’t have an audience," Fryman explains later. "Either we’re laughing, or we’re not laughing."

Traditional multi-camera sitcoms are shot like little plays, albeit with many fits and starts, before a studio audience. Producers and directors use the real laughter (and lack of it) to make a laugh track and determine how to modify the show, supposedly to make it funnier.

Most single-camera sitcoms, shot like movies, have no laugh track. How I Met Your Mother is an unusual hybrid, with different shooting techniques used for different scenes, and audience sounds added. Sometimes, a rough cut is shown to an audience to see where the laughs are, and modifications are made. But often, the audience at the table read is the only one the show will have before it airs.

"We’re listening, going with our gut, and then we trust ourselves in rewriting," Fryman says. They also have to accommodate the geniuses from the studio (Fox makes the show) and the network, who make suggestions after the reading.

While they palaver, the actors hang out on Stage 22, where the show is shot with enormous attention to detail. Notice the mechanic’s shop on tomorrow night’s episode. It has real parts boxes - six starters, seven alternators - and other authentic automotive paraphernalia decorating a set that will be used only once.

Monday morning begins the weeklong shooting process that will end Friday night, with more than a week of editing to follow. A CBS Web site has a day-by-day feature outlining how one episode progressed: Go to www.cbs.com/innertube and click on the show title and then "behind the scenes."

As the week passes, the days can get very long. "Arrivederci Fiero" arrives with an unheard-of 60 scenes. Seinfeld, considered pretty frenetic, rarely got to 30. Thursdays and Fridays, Fryman often doesn’t get home until after 10 p.m.

"If this had happened when my daughters were young, it would never have worked," she says. But now Megan’s a basketball star and Katie’s the eighth-grade class president, and they can get along alone pretty well, with the help of Fryman’s husband, writer-producer Alan Grossbard.

Fryman, 47, started in TV when she was two years older than her daughters, interning in Philadelphia at The Mike Douglas Show while she was still at Harriton High in Lower Merion. After attending Pennsylvania State University, she rode across country for fun with her older brother. By that time, Douglas had moved to L.A.

"I dropped by to say hello. They said, ’Want to work here?’ My mother thought I would be back at any moment. She still believes that, 26 years later."

Fryman eventually got into game shows and soaps. A friend and colleague, Peter Noah, thought she might be good at sitcoms. In January 1994, he invited her to direct an episode of his series, Cafe Americain, starring Valerie Bertinelli.

A little 6.7 Richter thing, the Northridge Earthquake, postponed production. "All the sets fell down," Fryman said. "Then, right before we did the show in front of an audience, they announced that the show was not being picked up."

No problem. That spring, Fryman directed three episodes of a summer sitcom, Muddling Through, featuring someone named Jennifer Aniston. Fortunately for her, that one tanked too, because Friends was casting. It was only a coincidence that Friends exec producer David Crane was two years ahead of Fryman at Harriton, but she did get to direct episode four, "The One With the East German Laundry Detergent."

"The word went out," she said. " ’Well, Pam’s done Friends.’ "

She has been a full-time sitcom director ever since, most notably helming 33 episodes of Frasier.

Fryman will return to Philadelphia in June for a joint high school reunion for the Harriton classes of ’76 and ’77.

And, in a group that has a professor of neuroscience at Rutgers University and another in immunobiology at Yale, she figures she won’t make too many ripples.

"I’ll just sneak into the back," she says, a far cry from her center-of-the-universe status on Stage 22.