The Insider.com

As polarizing as HBO's hit show Girls is, there is at least one thing everyone seems to agree on -- how integral the show's distinct, hipster twenty-somethings fashion is to the vibe of the entire show (so much so that even Vogue has done an article on it).

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And now the woman behind all the distinct season one looks, Girls costume designer Jenn Rogien, is dishing on main character Hannah's often talked-about fashion sense, why Adam's always shirtless, and the original inspiration for all the girls' styles.

"Hannah probably had the most obvious evolution because her look was going along with the growth of her relationship with Adam," Rogien tells Fashionista.com. "In the episodes where they are together, her look definitely takes on a little bit of influence from his world. His pajamas, his athletic wear, which I think Hannah would never wear [otherwise]."

Related: Who's That Hottie?! 'Girls' Star Andrew Rannells

As for Adam himself, she clarifies that his seemingly permanent shirtless status is actually derived from his character.

"It was requested in some of our very early meetings [that Adam not wear a shirt] before I had seen much of the script," she reveals. "I was very game, and Adam was very game. As we got [more of the] script we started to understand: he’s a carpenter, he wants to make cool things. It was a very specific part of his character."

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Much has been noted on the realistic nature of the characters' styles (unlike Sex and the City's notoriously high-priced designer duds) and Rogien confirms that a lot of the clothes are actually available for mass consumption.

"We go all over. It's very character-driven and it’s very script-driven and I want every piece to support the story, and for Girls specifically, we end up going places that would be realistic for the characters," she says about where she gets the clothes that end up being worn on the show. "There's a ton of vintage with a ton of thrift. We spend a lot of time in Williamsburg. We love H&M. We love Zara."

But of course there's the fashion moments that are one-of-a-kind -- such as Jessa's eye-catching blue suede shoes she wore to her surprise wedding.

"They were blue suede Alexander McQueen with the gold skull. Jemima and I both thought it was very appropriate in that it was a little bit of a nod to bridal tradition. It was a little punk, rock-and-roll, and it’s very Jessa to be very free-spirited and sort of follow the rules and then not follow the rules at all."

And what's the highest compliment Rogien has gotten from her work so far?

She's starting to see a lot more "Hannah" type fashion on the streets of NYC.

"I think I will always people watch all over New York City," she says about getting her original Girls inspiration from people-watching in Brooklyn. "It's also been really interesting to see a few things reflected back. We're starting to see a little bit of a Hannah look, but maybe it's just because of what I'm looking for. ... And I don't know if it's that they are or if it's that I notice, but it is fun!"