“Wait, am I dressing like a 14-year-old boy, or are all 14-year-old boys dressing like me?” she asks in that voice that sounds as if it belongs to a baby with really bad allergies. “Remember, they’re my demo.”

Well, part of it. There are also the young women who aspire to look “as cute as Sarah in geeky chic,” as one nose-ringed indie girl put it at Ms. Silverman’s book-signing at the NoHo Urban Outfitters in April. And of course there are the legions of middle-aged urban men who see in Ms. Silverman one of their more prominent dude fantasies: the hot tomboy-next-door who will laugh at your potty jokes, punch you in the arm and then make out with you. It’s almost embarrassing to witness the exchange between her and the waiter at the hotel. When she asks if she could possibly, maybe, please, have mint in her ice tea, he declares, “For you I find mint!” I’m not sure if he bowed as he handed it to her, but the bow was implied.

Ms. Silverman’s look is, in a way, an integral part of her comedy. It provides a buffer — the buffer of adorableness. The 39-year-old, who has been doing stand-up since she was a student at N.Y.U., has become famous with the most brilliant, jaw-dropping, deliberately shocking jokes about racism, abortion and rape. (“I was raped by a doctor ... which is really bittersweet for a Jewish girl.”) Somehow hoodies and pigtails soften the blow.

(I saw this buffering effect in action, when Ms. Silverman was doing stand-up in Midtown soon after 9/11. That night she suggested that American Airlines needed some help with its P.R., and should change its motto to “First Into the World Trade Center.” The crowd extended her the courtesy of a stunned silence, until one man in the front row barked with laughter. Then the audience started booing him.)

In fact, there is a tradition of beautiful women in comedy desexualizing themselves. Lucille Ball was a showgirl before becoming a comedian, but we don’t think of her as a great beauty; Phyllis Diller was actually a very attractive woman who donned the fright wigs and feathers to appear less threatening. “Apparently people can’t look at a pretty woman and listen to her at the same time — and you have to listen to funny women,” says Gina Barreca, the author most recently of “It’s Not That I’m Bitter” and a professor of English and feminist studies at the University of Connecticut, where she specializes in women and humor.

Not to say that Ms. Silverman’s hotness is unrecognized; she was, after all, No. 29 on Maxim’s Hot List in 2007. And in fact, it’s a delicate balancing act, because her beauty also lets her get away with being gross. Would she have been the filthiest, best joke teller in the 2005 documentary “The Aristocrats” if, as Professor Barreca puts it, Ms. Silverman “gained 40 pounds and dropped a litter?”

Of course, Sarah Silverman doesn’t quite see herself in a fashion tradition at all.

When she started performing in the early ’90s while a student, she had a whole ensemble: miniskirts, “That Girl” beehive, black buttoned shirts with sheer black sleeves. These days, she admits, “If I kill in an outfit, I’ll wear it again and again, until people start making fun of me.” But otherwise, she insists, her look is entirely uncalculated and just a reflection of her absolute need for comfort:

“There’s so many things you have to do in order to get dressed up” — starting with shaving her arms — “and heels put me in a bad mood after a certain amount of time. I hit a wall and I must go home.”

Besides, Ms. Silverman says, she comes from a long line of fashion goofballs: her father, who owned Crazy Sophie’s Factory Outlet in New Hampshire, wears only clothing with the Target logo on it, and her mother rocks overalls. At one point, when she was on the “Tonight Show” and her father and stepmother were in the audience, Jay Leno called them onto the stage; her father’s shirt had large visible stains. Said Mr. Leno to Ms. Silverman, “I see where you get your dress sense.”

“I’m not being modest or whatever, but I think I just look better in casual clothes,” says Ms. Silverman, who has a chapter in her book titled “Fear and Clothing.” “I feel like a transvestite when I’m all dressed up.”

Case in point: the gown she wore to the 2009 Emmys, a dress Mr. Hirshey calls “epic in its hideousness.” Badgley Mischka offered to design her dress for the occasion, and Ms. Silverman was thrilled. She picked a satiny fabric in cobalt blue. “I wanted to look like a princess,” she says.

But things quickly went wrong. At one of the fittings, she began to make adjustments. For one thing, she wanted her gown to have pockets. Then, she insisted the corset be loosened. Badgley Mischka insisted their name not be used in conjunction with the dress. (“I mean, Mark and James love her, they love her work,” says Rob Caldwell, the Badgley Mischka spokesman. “But she added fabric at the hip.”)

So Ms. Silverman happily told everyone it was the creation of Yuliy Mosk, the local tailor who did the fittings. (Mr. Mosk didn’t really want anything to do with it, either.) As one blogger wrote, “Sarah wore a royal blue strapless gown that looked like it was swiped from the fat girl in class who wanted to buy a dress that she could wear to both the junior prom and the Renn Faire wedding she had coming up later this summer ...”

But Ms. Silverman was unfazed, and still believes that dressing up is part of the patented Make It a Treat philosophy she expounds on in her book (described as “often hilarious and occasionally revelatory” in a review in The New York Times). Just about everything in life should be held in reserve for special occasions, she says.

“I do like dressing up as a treat, to feel like a princess,” she says. “If I did it all the time, dressed up with makeup, when I didn’t do it people would be like, ‘Oh my God, did you see what she was wearing, and no makeup?’ But if you dress like this all the time” — Silverman tugs at her tube socks — “and then you put on a little dress, people are like, ‘Heyyy, look at you!’ ”

Ms. Silverman says she does have a thing for sexy underclothes — “but like mostly at home, for one person.” That person, post-Jimmy Kimmel, is Alec Sulkin, a writer on “Family Guy” whom Ms. Silverman met on Twitter (his nom de Tweet: The Sulk).

“He was following me, and then I began following him, and I was like, ‘You’re funny.’ Wednesday is our 16 week-erversary. Tonight is our 110th sleepover date!”

With nothing more than a drop of Benetint on her cheeks and lips, Ms. Silverman looks easily 10 years younger than she is. But this year she turns 40. Uncalculated or no, she’s kind of wondering what’s next sartorially. “I’m not sure if pigtails and football shirts are going to fly. But I’ll find out. And I’ll let you know.”

As the waiter clears her glass of mint tea (repairing to the kitchen, presumably to lick the rim), I ask Ms. Silverman if there’s anything I’ve missed — any point in particular she’d like to make. “Yes,” she says, giving me a warm hug. “Jews run the media.”