In the first scene of the new series “My Big Fat Greek Life” (Sundays at 8 p.m. on CBS), Nia Vardalos inexplicably strikes up a conversation with the guy next to her at baggage claim. “Flight from Athens, huh? Me too. I was on my honeymoon!”

The man stares at her like she’s gone mad, but Nia doesn’t seem to mind. Minutes later, she’s hurtling over other people and bags in pursuit of her suitcase. She fails to retrieve it, plays it off, and walks back over to the stranger, saying, “Yeah, I’ve learned to trust that things’ll turn out OK. I’m just so happy! Do you speak English?”

This scene bears some resemblance to the movie “My Big Fat Greek Wedding,” but not much. The difference is, it doesn’t make any sense, it feels stilted, the physical comedy seems utterly out of place and it’s not that funny.

In other words, the difference is that it’s a sitcom.

Before “My Big Fat Greek Wedding” was released, expectations for it were relatively low. It started as a one-woman show, attracted interest from Rita Wilson and Tom Hanks, and was converted into a small, heartwarming movie with a simple story, the kind of movie that’s lucky to make back its $5 million budget. Instead, the movie was a smash hit, grossing more than $240 million.

But if exceeding expectations brings its own good press, falling short of expectations can be the kiss of death. Thus, “My Big Fat Greek Life” faces a very different challenge than its cinematic predecessor — the challenge of meeting those high expectations, paired with the difficulty of surviving in a sitcom market that’s feeling pressure from the increase in reality programming.

The good news is that all but one member of the movie’s excellent cast appears in the sitcom: Lainie Kazan and Michael Constantine return as Vardalos’ parents, along with Andrea Martin, Louis Mandylor, and Gia Carides. John Corbett, who played Vardalos’ husband, has his own show on FX called “Lucky.” So Steven Eckholdt, best known from his role in the short-lived ABC sitcom “It’s Like, You Know …,” replaces him.

The bad news is that USA Today reports that Vardalos “wants to reduce the old-world feel, making the family less obstinate and shifting away from such themes as the father’s idea that women shouldn’t go to college.” Yet that “old-world feel” was precisely what made the older audience around me break into uproarious laughter when I saw the movie in a packed theater months after its initial release. Hasn’t the success of “Seinfeld” done enough to prove that sitcoms don’t have to be populated by bland, likable characters?

But in keeping with Vardalos’ stated strategy, her big fat Greek family appears to be on Prozac. Their stern, overbearing demeanor has been replaced by warmth and smiles and cheery enthusiasm. The effect is unnerving, like watching Larry David sing “Sunshine on My Shoulder” at gunpoint.

Still, in some cases, this upbeat twist is handled well and brings its own laughs. After Nia admits that she and her husband don’t want the house her father bought them, her mother announces, dramatically, “Nia, you’re killing your father!” and slams the door behind her. A second later, she reopens the door and says, pleasantly, “Bake the casserole at 350.” The moment rings true, and still serves the purpose of teaching the audience that harsh words in this family can’t be taken literally. The show’s writers shouldn’t back off from those harsh words, though, or they’ll lose the story’s most interesting conflict: the struggle and old-fashioned acting out of a patriarch whose power has been supplanted, his adherence to Greek codes of behavior dislodged by the conventions of modern life.

There’s no reason why such a promising cast and premise should be watered down and neutered until it adheres to some 20-year-old sitcom formula, a formula of which viewers have clearly grown weary. When Nia goes to visit her pouting father at the restaurant, for example, the scene is so familiar from other sitcoms, it feels like déjà vu.

“I was just remembering your first day at that new school. You cried the whole time,” her father tells her. “Now, you don’t need me.” This revelation makes sense after an hour and a half of rising tension, but 20 minutes into a high-spirited romp, it’s like being handed the same old genre coloring book for the umpteenth time. Our crayons are worn down and we hardly care.

And why must Constantine switch from stubborn old mule to warmly communicative father within seconds, with dialogue that’s painfully on the nose? When Archie Bunker or George Jefferson or even Fonzie had a moment of weakness, it was obscured in layers of defensiveness and confusion. As an audience, we recognized that, when Archie said, “Jesus Christ,” and then pouted in his favorite chair, or George kissed ass, or Fonzie started to reluctantly mouth the first consonant in “Sorry,” we were seeing a limited character doing his best to express himself. No matter how pathetic his attempts might have been, we understood it, and we enjoyed it more than if each character had spewed forth a poignant anecdote every time the tension heated up past lukewarm.

The popularity of “Everybody Loves Raymond” proves that audiences are perfectly willing to embrace a cast of inexpressive curmudgeons. Americans have all varieties of passive-aggressive grouches in their own living rooms, so why would they want Mike and Carol Brady on their TV screens?

Admittedly, though, sitcoms rarely hit their stride until halfway through the season, and Vardalos’ ability to adhere to the conventions of the form may reflect her skill as a writer more than anything else. If the show gathers an audience, she may find herself making bolder choices that could transform a passable show into a unique and entertaining comedy. Hints that she’s willing to take risks are certainly there, as when Nia’s aunt feels compelled to offer her husband sex tips. “Thomas, women have zones. Call me, I have a book.”

If the characters and conflict of “My Big Fat Greek Life” continue to feel true to life, while regaining some of their edge, things might just turn out OK. Nia, at least, has learned to trust that they will.

“A Few Minutes With Andy Rooney” debuted on “60 Minutes” in 1978, and in the 33 subsequent years, the segment’s namesake gained a reputation for being television’s most curmudgeonly broadcaster. But in his final scheduled on-air comment Sunday evening, Rooney betrayed the sentimentality of someone less surly than he’s been reputed to be: ”I’ve done a lot of complaining here, but of all the things I’ve complained about, I can’t complain about my life. [...] All this time, I’ve been paid to say what’s on my mind on television. You don’t get any lucker than that.”

Apparently it’s going to take more than the threat of assassination to wipe the smile from of Dave Letterman’s face.

The “Late Show” host returned to work Monday night. It was his first broadcast since the news surfaced last week that a would-be jihadi had called for his death on an Internet message board. No stranger to controversy, Letterman seemed nonplussed by the threat. The comedian deftly illustrated that point by enumerating all the individuals and parties who openly hate him — a list that includes most humans and animals.

As if CBS’ new “Two and a Half Men” naked promo wasn’t enough to convince audiences that next season is going to be for adults only (“No kids allowed! Sorry, Angus T. Jones!”), today’s plot leak regarding a certain character’s certain demise in a certain type of “meat explosion” should do the trick. (Sorry, I didn’t want anyone to get upset over spoilers.)

Appearing on CBS’ “Face the Nation” Sunday, Treasury Secretary Timothy Geithner spoke out against lawmakers like Michele Bachmann who have claimed the administration is using scare tactics to over-hype the debt crisis.

“On Aug. 2., we’re left running on fumes,” Geithner told host Bob Schieffer. “We have no capacity to borrow… We have to act; Congress has to act ahead of that point. If they don’t act, then we face catastrophic damage to the American economy.”

1. PETA pets of the day: Kristen Wiig and Russell Brand were named Sexiest Vegetarians of 2011 by the animal activist group. Now how long until they try to convince the stars to pose naked?

2. Actual nudity of the day: The Gloss’ Jamie Peck walked around topless in Central Park to prove that it’s legal for women to go shirt- and braless in public under N.Y. state law.