Tonight, teen queens Serena van der Woodsen and Blair Waldorf will party-hop with Vogue editors at Fashion's Night Out, the shopping event that helps kick off New York Fashion Week.

At least that's how it will look to viewers of teen drama "Gossip Girl" on Monday and Sept. 27. The Fashion's Night Out episodes, filmed well in advance of the actual event, reflect how intimately the television show has come to associate itself with the fashion industry. When the new season of the show begins next week, fans may be curious about what's going to happen to Blake Lively's Serena and Leighton Meester's Blair. But the show also devotes considerable energies to a different question: What will they be wearing?

FASHION'S NIGHT OUT

Over the summer, Ms. Lively spotted a dress by British designer Jenny Packham online and lobbied costume designer Eric Daman to get it for the show. For the Fashion's Night Out episodes, Ms. Lively (pictured right), will wear the Fall 2010 long-sleeved silk chiffon dress with an embroidered collar and waist.

"It's a very unusual dress," Ms. Packham says, noting that it has a floor-length hem, a slit cut to the waist and a deep neckline. In part to due to her design's appearance on the show, Ms. Packham chose to have her collection make its New York debut on Monday, the same day the new season of "Gossip Girl" begins.

PARIS

Before the characters attend Fashion's Night Out, they open the season in Paris. There, Ms. Lively sports a pale-pink cage dress by couturier Georges Chakra, who debuts his collection at Lincoln Center today. The dress, embroidered with more than 170,000 Swarovski crystals, is accessorized with men's dress shoes and a slouchy jacket.

"It's a new way of wearing couture," Mr. Chakra says, of styling his dresses into a casual look. (Even with a $48,000 price tag, two cage dresses were sold to customers in Russia and Dubai.) The designer hopes that daughters of his couture customers might be inspired by Ms. Lively's look, noting he recently completed a private "Gossip Girl"-inspired couture collection at the request of a client whom he describes as "a princess."

Costume designer Mr. Daman played off Parisian grays with bursts of color, dressing Ms. Meester in a bright orange Oscar de la Renta gown and Ms. Lively in a gold Pucci jacket paired with trousers in Yves Klein blue ("like a superhero Gossip Girl"). Mr. Daman says a Moschino multiprint dress represents Brigitte Bardot and Parisian boho chic as distilled by Blair Waldorf. The cherry-printed silk dress with an attached scarf is accessorized with a mint green beret, Chanel cuffs and shoes and a Chanel hobo bag.

Mr. Daman also chose two dresses and a tuxedo jacket from French designer Maxime Simoens, who at 25 is a relative unknown. Mr. Simeons's clothes are not yet sold in the U.S., which he hopes to change after his dresses make their television debut.