By Lauren A.E. Schuker, wsj

For “Mad Men” creator Matthew Weiner, it was instant intrigue. He first noticed Janie Bryant, the show’s costume czarina, in an office elevator three years ago. The Tennessee-born stylist, who had recently finished designing late-19th-century costumes for the American Western series “Deadwood,” was on her way to interview with Weiner, but both were unknown to each other at the time. Bryant was sporting a gargantuan belt buckle. “It was like something a prizefighter would wear,” Weiner says. “I thought, ‘How bold. How cool.’ ” It didn’t take long for Weiner to make a decision after the two-hour interview that followed—he hired her two days later.

Weiner went to film school at USC, and then spent several years finding his way in Hollywood before he got a taste for period pieces writing for a CD-ROM that accompanied Oliver Stone’s “Nixon.” Afterward, he wrote for various short-lived comedy shows until the idea for a series about a 1960s ad agency came to him in 2000. While no one wanted it at the time, it helped him land a spot writing for, and then producing, “The Sopranos.” That notoriety finally got his pilot made in 2007.

With its fourth season debuting in July, the AMC show has not only reshaped television, it has also inspired the fashion world, popularizing the clothes of the era, from sharp suits to fitted dresses.

Bryant’s childhood experiments with fashion (her dolls were very well-dressed) flourished in her 20s, when, after studying painting and fashion design in college, she worked for designer John Scher in New York (they shared a love for ’60s tent dresses). Her move to costuming began with a nostalgic television ad for Nick at Nite before a string of independent-movie jobs led her to “Deadwood.” Last year, she created a limited-edition “Mad Men” suit with Brooks Brothers, which had helped her make some costumes for the show. Banana Republic has an ongoing partnership involving its fall “Back to Work” line, and Bryant has her own women’s line coming out later this summer. It will be contemporary, she says, “but I am always inspired most by historical looks.”

While fashion may have inspired Bryant and Weiner’s collaboration, it’s a stubborn perfectionism that has sustained it. “We both give each other a hard time,” Bryant says, sporting what she calls her “go-to outfit” on set: black Valentino boots, skinny jeans and a black leather jacket. Weiner admits he can be a tough boss, with a temper that, until recently, kept him from buying a BlackBerry for fear that he’d lose his cool and write something too strident.

“Matt has a very strong opinion of what he wants in terms of clothes and he’ll write it into the script,” says Scott Hornbacher, the executive producer of “Mad Men.” “But Janie is one of the only people on set who can wear him down. She’s got that Southern aspect to her—where everything is said in a very polite way with a smile—but deep down she’s pretty tenacious.”

WEINER ON BRYANT

Everyone thinks that Janie’s job consists of picking cool clothes, but she’s really a storyteller. She cares about who the character is and what we are trying to say about them. If I write a fur in there—say, Don gives Betty a fur—I know that we can develop a history of that coat and how it relays a bit of the sad story of their marriage.

Because Janie grew up in Tennessee, she is very attuned to formality and the way that things stay pretty much the same the further you get from Los Angeles or New York. People don’t always change with the times. Part of the story that we are trying to tell is about the loosening of all this stuff—the crudening of manners and style as the period changes. Janie and I talk about that all the time and try to signal it in little ways, like with a character taking off his hat in the elevator. It’s unusual for a costume designer to stay on this long, and that means so much since here continuity really matters.

Every single person on “Mad Men” wants Janie to make them something to wear in real life. She has made my wife a Chinese sheath dress. Whenever I take a picture on set, I bring two sport coats and make her choose. So I’m very happy she has her own line and that good things are happening to her. And while I’m not a jealous person, or a competitive person, I hope Janie is most famous for what she’s done on the show.

BRYANT ON WEINER

I am always inspired by Matt’s words. He writes part of every episode and he is really hands-on. Sometimes I’ll show him some of the costumes and he’ll insert a line for the character about the clothes. It’s such a hand-in-hand thing: Designing and writing are so intricately connected.

We’re tough, we disagree, but it’s always in the spirit of improving the show. One of our bigger disagreements came in the third episode of last season; Betty wears this lace dress to the Derby. I showed the pictures to Matt the day before we were shooting the scene, and he starts going off about how the lace looks matronly. But I find it elegant, and lace is my favorite—eventually I won him over. Matt always talks about people getting stuck in certain styles and Betty being stuck in high school. Betty would never sport bell-bottoms in the ’70s; she’s not that kind of lady.

I definitely do a lot of research. I go to the library at Western Costume, look at old catalogs, magazines, books. I stay pretty separate from the writing—I am all visual. One time, he asked me if I wanted to come to the writers’ room, and I said, “Absolutely not.” Matt is the opposite: He can do both. I have asked him before, “Hey, do you want to change jobs?” He would probably get into it. It’s a big relief when he comes on set and texts my phone to say, “Betty looks amazing!” At least it’s better than the reverse.

People have responded to the show by embracing a dressier lifestyle, especially men with a more tailored look—I love that. I always felt like it was the highest compliment that the show changed menswear more than women’s clothing, because men are much slower to change. That was never the intention, of course. “Mad Men” was never meant to be a fashion show.

Edited from Schuker’s interviews with Weiner and Bryant

Sources: “Mad Men” season 4 premieres on AMC Sunday, July 25, at 10 p.m.,