The Big Bang Theory is huge. Now in its sixth season, it reigns as the hottest sitcom in the US, and now hotter than ever with an average 19 million viewers each week there.
As almost every viewer knows, Big Bang centres 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. Maybe she doesn't always get what the guys are talking about. But in that way she represents most of the world."
Reflecting on what her hit sitcom has meant to other parts of her life, she mentions her parents - her father, a real estate agent who has weathered tough times, and her stay-at-home mum in Southern California. Cuoco, who turned 27 last November, grew up happy to be the centre of attention.