America - without quite knowing it - watches them at work from 8 to 9 every Tuesday evening. They're the Marshalls, and their work - "Happy Days" and "Laverne and Shirley" - resembles a filtered version of their lives. They're television's First Family, and these are the Marshall Chronicles.

Meet father Tony, mother Marjorie, son Garry and daughters Ronny and Penny, America's two most popular work from 8 to 9 every Tuesday eve-TV series are their babies. "Happy Days," home of Fonzie and the Cunninghams, placed first in the ratings last season and ranks second this year. It was pushed out of first place by its own spin-off, "Laverne and Shirley" - America's weekly fling with two brewery bottle-cappers in Milwaukee circa 1960.

So far this season, an average of half the homes watching television on Tuesdays have tuned in to the Marshall duo. (Tonight a 90-minute "Happy Days" rerun preempts "Laverne and Shirley." First-run episodes of both shows are being hoarded for use next month, a crucial ratings period).

Not since the Nelsons has one family affected so many televised fantasies. Unlike the Nelsons, only one of the Marshalls - Penny - actually is on the screen. She plays Laverne. But her brother Garry is the real boss. He was the most active partner in the creation of both shows and remains more responsible for them than anyone else.

As co-executive producer of the shows. Garry hired Tony as a producer. Penny as a star and Ronny as a casting director and associate producer. He uses his own children in one "Happy Days" each year and his dogs in the credits for "Laverne and Shirley."

Have we left anyone out? We certainly have. Over all of this, mother Marjorie Marshall watches with an eagle-eye. This TV juggernaut is just a shuffle and a slide away from her two-bit dancing school (literally two bits a lesson) in the Bronx.

Marjorie Marshall sat front and center at a dress rehearsal of "Laverne and Shirley." She was surrounded by the very young, who are allowed to watch this particular session each week without older guardians in tow. Occasionally she threw a dirty look at the noisier youngsters. Occasionally she

Still, she smiled and waved when she was introduced to the audience. And she seemed to appreciate it when Garry approached her and warned that Penny would take a bigg fall in this episode. Sure enough. Penny took a spectacular stumble down a ramp. The crowd roared, and Marjorie Marshall joined in. But then she muttered quietly: "Some time something's going to hurt her."

The Marshalls are troupers and it was their mother who trained them to be that way Marjoire Ward was already teaching dancing when she was barely a teenager, and Tony Marshall says she was attracted to him in high school "because she thought I was a good dancer."

It's hard to imagine Tony tripping the light fantastic with Marjorie.

He spent most of his career in advertising most often as a maker of industrial films. He maintains meticulous files on his children's accomplishments and he wears a prim dark suit to his office on the Paramount lot. His dignified presence seems a bit out of place - "We shoot holes in dignity," points out his son. But Garry values Tony's service. "I spend money and he saves it."

The stately executive and the madcap dancing teacher were married in 1931. Garry was born three years later, Ronny arrived four years after Garry, and Penny six years after Ronny. No Miss Twinkletoes

The children weren't as quick on their feet as Mom. Garry was "a klutz," he recalls, and wound up playing drums for the Marjorie Ward Kiddie Revue. His other teen activities included the Bronx - Falcons - "a group disbanded by New York Police in 1951," notes his official bio - for which Garry used the name Gino Marscharelli (the last name was Tony's father's when he immigrated to America). "Happy Days" is a sanitized, Midwestern version of his teen years, he says, and Fonzie is drawn from several friends, particularly the one with the motorcycle.

Neither of the girls was Miss Twinkletoes, but they kept dancing. Their mother would take her troupe into a show at the slightest excuse - "if a stranger on the subway asked her," says Garry. Once they did the Gleason show.Naturally, the kids all read Variety.

On rainy Wednesdays Mom would pull her brood out of school and herd them into Broadway matinees. They would take a lunch and sit in the balcony. Penny remembers "the tuna reeking through the theater during "The Miracle Worker." Usually they would stick to comedies and musicals. Mom didn't like anything heavier unless children were involved, as in "The Miracle Worker."

Her two eldest went to Northwestern - Garry in journalism and Ronny in radio-TV. Then Garry worked for the Army and the New York Daily News, and Ronny for the Nielsen ratings service and the Screen Actors Guild.

Garry broke into the bigtime as a gag writer for Jack Paar and Joey Bishop. This led to a writing partnership with Jerry Belson, churning out scripts for the Danny Thomas, Lucy and Dick Van Dyke shows. Like most TV writers, Marshall wanted to produce. But a vet endowed him with these words of wisdom: "Every Lucy show you write is an insurance policy for your kids' education," he was told. This has been literally true, he reports.

Finally, however, Marshall and Belson sold a series, "Hey, Landlord." It lasted a year. "Me and the Chimp," one of TV's most scorned flops, didn't even last that long. But it was worth the humiliation, for it was Marshall's first collaboration with Fred Silverman, then at CBS. Later they would create "Laverne and Shirley." And less happily, "Blansky's Beauties."

Marshall and Belson finally made it big with "The Odd Couple," which lasted five years. The series also introduced Penny Marshall to the world. Needling Nepotism

Penny had gone to the University of New Mexico - "because my mother though it was closer to New York than Ohio" - but dropped out after two years. Garry asked his sister what she wanted to do. She remembered the time she was plucked out of a dancing role to appear as Ado Annie in a New Mexico production of "Oklahoma." Maybe she could be an actress?

Okay, said her big brother. After penny had appeared in such roles as "the "before" in a "before/after" shampoo commerical ("after" was played by then unknown Farrah Fawcett), she became a familiar face as Oscar's secretary on "The Odd Couple." Garry concedes it was nepotism to hire her.

But others hired her too - as Paul Sand's sister-in-law on his series, and in many guest appearances. By the time Laverne came along, nepotism wasn't needed.

The Marshalls grin and bear it when the topic of nepotism comes up. A few weeks ago "Laverne and Shirley" presented a whole episode on the subject, and filling two of the smaller roles were the mothers of Penny and co-star Cindy Williams.

We work better if we know and like each other, say the Marshells. Yes, there are a few awkward moments, especially for Penny. When the actors gripe, as actors must, about "the stupid writers," she says, "half the time they're talking about my family. I feel both sides." And Garry says "I forget Penny should be treated liked a star sometimes and not like sister."

Tony scoffs at such talk. "I don't like this word 'nepotism,'" he declares, pointing out that whatever the family ties mean, they work: "This family has a hit." He adds: "I think we're the happiest family in the TV industry. And I mean the whole cast and crew." Garry encourages everyone to think of their friends when has to hire, and several pals from the old bronx neighbourhood work on the show. So does the ex-New Mexican who cacast Penny in "Oklahoma." The Old Bronx Recipe

The old Jewish-Italian neighbourhood is present in other ways, too. The "shmiel-shmazel" routine in the credits of "Laverne and Shirley" in straight off the streets of the Bronx. The "milk and Pepsi" blend Laverne drinks was a Marjorie Marshall recipe: Her children's Jewish friends who couldn't drink milk with me at the dinner table drank Pepsi instead, and the Marshall kids were jealous. So Mom added Pepsi to the milk - "it all goes to the same place, she explained.

If the Marshalls' life in the Bronx has affected television, the Marshalls' life on TV has also affected the Bronx. Garry recently visited the old neighbourhood and took a look at the basement ballroom, now deserted, where his mother's students once tapped away. Someone had scrawled "Fronzie" on the wall.