NEW YORK (AP) -- "I know this sounds like it's not true," says Kaley Cuoco, "but as huge as the show is, it's just part of my life -- not my whole life."
"The Big Bang Theory" is huge all right. Now in its sixth season (airing Thursdays on CBS at 8 p.m. EST), it reigns as TV's hottest sitcom, and now hotter than ever with an average 19 million viewers each week.
As virtually every viewer knows by now, "Big Bang" centers on a gaggle of geeky Cal Tech scientists, chief among them Sheldon (Jim Parsons) and Leonard (Johnny Galecki), apartment mates who, by great good sitcom fortune, live across the hall from Penny, played by Cuoco. Penny aspires to be an actress but pays the rent by waiting tables at a Cheesecake Factory.
Unlike the boys, Penny is no genius. But neither is she a dumb blonde, which is key to the genius of "Big Bang."
"She's obviously not book-smart," says Cuoco, "but she's street smart and good-hearted and can make fun of herself. The producers never made her ditzy. Maybe she doesn't always get what the guys are talking about. But in that way she represents most of the world."
It was pretty smart to make Penny the "normal" character through whom the audience can enter the abstruse, brainy realm the guys occupy. At the same time, sexy Penny presides as a universal object of desire.
Cuoco is totally up to the task of playing such a gal. During a recent mid-afternoon interview, she is hearty and self-possessed and comfortably glam.
She orders a vodka martini -- "straight up, very cold, with a twist," she tells her waitress, then explains to the reporter, "My new drink. My new thing."
All that, plus she has a sentimental streak.
Reflecting on what her hit sitcom has meant to other parts of her life, she mentions her parents -- her dad, a real estate agent who has weathered tough times, and her stay-at-home mom in Southern California. During her childhood, they often had to cut corners, she says, "but I never noticed when things weren't great.
"This year, I'm hosting Thanksgiving and Christmas with, like, 25 people at my house -- I can do that now." Her voice starts to tremble and her eyes moisten. "It's emotional, cause I remember we could never afford that. The show has been the hugest blessing."
Cuoco, who turns 27 on Nov. 30, grew up happy to be the center of attention.
"I was always very silly and never took myself seriously," she recalls. "When my father had the camera out, I'd be up close and annoying. My father would keep saying, 'Move back! Move back!'"
Her parents were supportive when she wanted to try acting, "but if I wanted to audition, I had to play tennis" (at which she excelled as a teen). "If I played tennis I had to be in a dance class. I always had multiple activities, so I never had to count on any one of them to feel successful."
She landed a role in a 1992 TV film starring Donald Sutherland. She played Maureen McCormick in the 2000 TV film "Growing Up Brady." Along the way, she landed jobs in lots of episodic shows.
But by 2002, she was feeling discouraged. She hadn't worked in a year.
Then her agent phoned about a project called "8 Simple Rules for Dating My Teenage Daughter." Reluctantly she auditioned for the part of the older daughter in a household whose loving but bewildered dad would be played by John Ritter. Cuoco got the role.
Though it built into a hit for ABC its first season, "8 Simple Rules" is remembered mainly as the final project of the beloved Ritter, who died abruptly early in its second year. The show pushed on through a third season, but it never overcame Ritter's tragic absence.
"I just adored him," says Cuoco, unleashing a stream of memories of how he used to cut up on the set and how much she learned from him.
"He'd put a potato chip on his shoulder and go, 'Do I have a chip on my shoulder?' And we would just crack up! He would do it every day!
"Working with him showed me that I loved sitcoms," she goes on. "I'm a 'Bridesmaids' type of girl. I love silliness. That's who I am at heart, and I know I can do it. If my career path takes me elsewhere, that's great. But comedy is my forte."
"Big Bang" co-creator Chuck Lorre, who snagged Cuoco for the show, agrees.
"Kaley was born to the form," he says in a separate interview. "There's an instinctive thing with comedy that some people have -- an elegance and gracefulness, where no effort is apparent."
But there's effort for Cuoco, and on the job it pushes her to question everything.
"How could it not?" she says with a laugh. "I wonder, 'Why did I do that line that way?' And I also constantly think I'm fat and hate my teeth. But I've gotten better over the years. I've started to accept." She smiles, revealing nothing remotely wrong with those teeth. "It's going to be fine."
EDITOR'S NOTE -- Frazier Moore is a national television columnist for The Associated Press. He can be reached at fmoore(at)ap.org and at http://www.twitter.com/tvfrazier