"They are about as un-identical as twins can be." That's Sarah Jessica Parker, talking to David Letterman on Tuesday night about her twin girls, Tabitha and Marion. "They are physically, intellectually, spiritually, geographically, politically, ideologically and religiously as different as two small 6-month-olds could be," the actress joked as Dave held up a picture of the tots. And how is she handling such a major change in her household, which includes 7-year-old James Wilkie and husband Matthew Broderick? "It's the most perfectly overwhelming experience," Parker eloquently tells People magazine. The key to managing the chaos: staying on a strict schedule, which helps her juggle parental duties with professional ones, like tirelessly promoting her Hugh Grant romcom, "Did You Hear About the Morgans?" Just don't ask her about the clichéd notion of bringing home the bacon and frying it up in a pan. "There are other mothers that are far better equipped to answer that question," the star assures OK!. "It's wonderful. It's fantastic. It's thrilling. You should ask all those other mothers. They do it, too, and they do it with less help probably, right? And far fewer rewards."