By StyleWatch
Updated January 13, 2010 10:00 PM

Louis Burgis/Retna

The man behind the fashionable style of Gossip Girl says the secret behind maintaining the cast’s physique is simple: underwear. “There’s a whole under-architecture system that happens on this show and on TV,” Eric Daman, costume designer for the fashion-forward show, told PEOPLE. “There’s a whole architecture that makes your boobs look great and your [rear] look great — just get some really good underwear and you’re good to go.” Daman, who celebrated the recent release of his book You Know You Want It at a bash hosted by Leighton Meester and Ed Westwick at New York’s Henri Bendel, explained that he works closely with the girls to create a unique look for each character. “I’ve been working with them since day one and we have a really great rapport together,” Daman said. “I’ve helped them become fashion icons and they’ve helped me become who I am and it’s a great give-and-take.” Which means that, yes, the actors do get to weigh in on what they wear on-screen as well as find inspiration for their off-screen lives. “I go to fittings with them and they see all these beautiful things and sometimes they say, ‘Oh, I love that. I want to wear that to my next rock concert’ but it’s not necessarily their characters. It’s about making them feel great and look great and staying true to the show,” explains Daman. And the most fun character to dress on the show? “Ed [who plays Chuck Bass],” the designer said. “Just because it’s nice to be able to take men’s fashion to a whole new place. With girls’ fashions, you can always have fun and play with it, but taking straight men’s fashion to this strange, dangerous place with very handsome, rich men drinking bourbon and wearing pink ascots — that’s a very big movement for American men’s fashion.” But there is one show that Daman won’t be designing for anytime soon — reality smash hit Jersey Shore. “No, absolutely not,” Daman joked. “What would I offer to Jersey Shore? They don’t want to look like this. They don’t want to look like Gossip Girl.” And as he points out, “I pretty much have a dream show to style and I would not trade it for the world.” –Joyce Chen