EAST HANOVER, N.J. — Relaxing in a pedicure chair one October morning here at a favorite nail salon, Nicole Polizzi, the diminutive troublemaker and reality-TV star known as Snooki on “Jersey Shore,” was explaining that she would wait until her infant son, Lorenzo, was 15 or 16 before sharing with him her goofy, boozy escapades from that MTV series.

“That’s when kids start to go out and have their first drink, go to parties and things,” said Polizzi, 25, who had recently returned from a tanning-products convention in Nashville, Tenn. “I’m going to say: ‘You know what? Mommy was just 21 years old, doing what everybody else does. She just had a camera following her.’”

Polizzi seemed to know exactly what she’d be doing in some far-off future, when she is laying down the rules rather than flouting them. But when it came to the nearer term — basically, any time after Dec. 20, when MTV will broadcast the final episode of “Jersey Shore” — she expressed an uncertainty shared by her soon-to-be ex-housemates.

“Because ‘Jersey Shore’ made us,” she said, “so it’s like, what now?”

Incredibly, it was only three years ago that MTV ran its first episode of “Jersey Shore,” its documentary-style account of four muscle-bound guys and four impossibly orange women partying down and hooking up in Seaside Heights, N.J.

Over six rapid-fire seasons, including excursions to Miami and Florence, Italy, “Jersey Shore” became one of MTV’s biggest hits ever, drawing nearly 9 million viewers an episode at its peak and introducing terms like “smooshing” and the gym-tanning-laundry shortcut “GTL” (among less savory acronyms) to the American lexicon.

The series has also elevated its distinctively monikered cast members like Michael Sorrentino (aka The Situation), Jenni Farley (JWoww) and Paul DelVecchio (Pauly D), making them the envy of unemployed milliennials, the scorn of Italian-American advocacy groups and unlikely ambassadors of their hurricane-devastated coastal escape.

But now these improbable celebrities are bracing themselves for a different kind of reality, when the parties and press tours — and the cornerstone TV show that supported them — go away, leaving viewers to take stock of why they tuned in, and its subjects to wonder if their fame could fade as rapidly as it arrived.

“We were regular people a couple years ago,” said Vinny Guadagnino, a “Jersey Shore” star. “I don’t want it to stop.”

At an Italian lunch in the West Village with the other men of “Jersey Shore,” Guadagnino said MTV had been vowing to cancel the show almost from its first season, possibly to see how the housemates would react. “We always think they’re bluffing,” he said.

Chris Linn, MTV’s executive vice president for programming, said by telephone that the decision to end “Jersey Shore” — for real — came down to its cast “moving on to the next stages of adulthood.”

With milestones like the birth of Polizzi’s son and Farley’s engagement, Linn said, the series “was moving away from the original conceit, and rather than drive it into the ground or milk it to the very, very end, we wanted to give it a dignified send-off.” (In a current season more about personal reflection than gratification, the show has also seen its numbers ebb to less than 4 million viewers an episode, though it remains strong among the younger audience MTV covets.)

When that final day of taping “Jersey Shore” occurred in the summer, and its housemates were allowed for the first time to interact directly with crew members and onlookers, “I had a nervous breakdown in the middle of the street, crying,” Farley said. “It was so bittersweet. That’s the house that changed my life.”

Sorrentino, who is gentler and more humble since a stint he did in a substance-abuse rehab program this year, agreed, in his own way, that “Jersey Shore” had not always allowed its ensemble members to display their full range of emotions and abilities. “We’re all very dense human beings with lots of different facets,” he said. “And I think you only get to see that one side — the party side.”

Perhaps more than their constant falling down, their drunken fistfights and shouting matches, it was the cast members’ rare aptitude for expressing themselves, candidly and without varnish, that won them acknowledgment from President Barack Obama and fans like Leonardo DiCaprio.

Maybe it was the way they reaffirmed viewers’ understanding of a certain middle-class vacation culture, or introduced it to audiences who found it completely alien. Or maybe, as the “Jersey Shore” executive producer SallyAnn Salsano argues, the series took the place of coming-of-age dramas like “Beverly Hills 90210” or the John Hughes movies from her youth.

“For all of their faults they’re actually really good kids,” said Salsano, who is 38 and spent many summers in Jersey Shore share houses. “I did the same thing. I lived in my parents’ house in my mid-20s, making more money than my dad, but they were making my lunch and putting gas in my car.”