Those outside the tight-knit fashion PR community might be familiar with Paul Wilmot, who sold his firm to Omnicom's Fleishman-Hillard; HL-Group, which got snatched up by MDC; or People's Revolution owner Kelly Cutrone, who through reality TV demystified the frantic nature of fashion-show seating and swag-labeling.

But inside the sartorial bubble live some highly influential shops unfamiliar to those outside the industry. Despite their insular existence, they're responsible for a majority of the runway shows and presentations that make Fashion Week, which kicks off on Feb. 9, possible for clients, buyers, media and an insatiable pop culture. Here we look at three of them.

PR CONSULTING
Pierre Rougier, founder of PR Consulting, forged his first connections as communications director of Japanese clothing manufacturer Onward Kashiyama. His early client roster featured Helmut Lang, a then up-and-coming Narciso Rodriguez and his former employer. But arguably his biggest break came not from working with a cutting-edge designer but from one of the most mainstream marketers out there: Procter & Gamble.

Mr. Rougier had been busily building his practice -- he spent 18 months doing PR out of a cramped one-bedroom apartment -- when P&G came knocking. He was initially hired to support the U.S. launch of Vidal Sassoon but the project eventually grew into P&G's entire prestige-beauty portfolio (Gucci, D&G, celebrity fragrances, etc.), and "shaped the way the company should grow," said. As Sylvie Picquet-Damesme, who joined Mr. Rougier's practice as partner in 1999, puts it, "It gave us the corporate vision. We didn't have it. When it's P&G you can't just say, 'We want to do this because I feel it.' It forced us to get that kind of thinking."

Soon after, the firm went low-end but high-style, supporting the launch of H&M in the U.S. in 2000 and riding the wave of accessible fashion. Soon it was applying what it had learned with H&M and P&G to clients such as Vera Wang. "It was an awakening that Vera Wang -- which is obviously a household name and custom bridal -- could offer a service of that level of runway and high-fashion [while also designing for] David's Bridal, Kohl's and Men's Wearhouse," Ms. Picquet-Damesme said.

In 2004, PR Consulting launched a lifestyle division with clients Thomas Keller and The Morgans Hotel Group. "Business was good," said Mr. Rougier. The U.S. had become a bigger player in the international fashion scene and fashion brands were doing more events and marketing around Mercedes-Benz Fashion Week. Around that time, the firm also hired Stephanie Cangiano Milia from L'Oreal to run the beauty business and bring a more corporate sensibility to the firm.

Though the agency is less dependent on high-end fashion, with clients such as Joe Fresh, Mr. Rougier said that hasn't eroded its edge -- or its roster. What's next? A deeper dive into digital and expansion in the U.S. "It's a trend to open everywhere, but we'd rather grow here," said Mr. Rougier.

KCD
Since it opened as Keeble Cavaco & Duka in 1984, KCD has retained its mix of clients on both the high and lower ends of the fashion scale, its philosophy on "fashion purism" -- meaning that it doesn't dabble in other industries -- and its unique pairing of fashion PR with production.

Co-founder John Duka died in 1989 and his wife and co-founder, Vogue editor Kezia Keeble, died a year later. Another founder and former stylist Paul Cavaco, who was also married to Ms. Keeble at one point, left in 1991 for Allure, where he was named creative director. Ed Filipowski and Julie Mannion, who had joined the firm in its early years, took over as co-presidents.

"We made a conscious decision in the early '90s that we were not going to diversify into other categories," said Mr. Filipowski. "We didn't want to have a hotel division or food, which was hard to leave in the '90s, as it seemed to be a way of growth at the time."

Fortunately for the new leaders, globalization created "a considerable boom." The U.S. was becoming a player in the European fashion scene and vice versa, said Mr. Filipowski. Marc Jacobs, who worked with the firm early on when he was designing for Perry Ellis, eventually launched his own collection and became lead designer at Louis Vuitton. And with American designer Tom Ford taking on lead creative roles at Gucci and Yves Saint Laurent, the firm's new partners knew it was time to open a Paris office. "It extended the influence of our agency in a very high-profile way," Mr. Filipowski said.

Today, KCD's roster includes Peter Som, Jason Wu, Tommy Hilfiger Men's and Women's, Diane Von Furstenberg, Marc Jacobs, Anna Sui, Calvin Klein and Victoria's Secret. Now the key to continued growth for these brands and prospective clients isn't globalization but digitization.

The firm launched a digital division 18 months ago to "find ways to create a balance between the integrity of fashion and new technology," Mr. Filipowski said. The internet "brought a democratization to fashion that didn't exist before. Ten years ago, 10% of what we did was digital. Now, 80% is done digitally."

KCD is launching its own digital tools, such as digitalfashionshow.com, a platform to create exclusive shows that target editors and buyers with unrelenting Fashion Week schedules. The biggest endeavor will be a "digital-driven" London office in late spring. The firm recently tapped Nan Richards, former president of Turner Broadcasting System Europe, to spearhead its growth strategy in Europe and the U.K.

BPCM
When former coworkers Vanessa von Bismarck and Carrie Ellen Phillips came together in 1999 to start a PR agency supporting artists, they paid the fashion world little notice. "We were less concerned with hemlines and more concerned with helping businesses," said Ms. Phillips.

But fashion and art were starting to come together in a big way, and after the partners realized that artists weren't the most stable of clients, they took on their first fashion account. German label Strenesse was a longshot, but they won the account and launched the brand in the U.S.

The client gave the firm fashion roots, but it also taught the partners what not to do. The team was selling a commercial line in the U.S. but it was also showing a runway collection that wasn't available in the region, so "PR and commerce were not in step," said Ms. Phillips. Ms. von Bismarck added: "If the stores are supported by a brand and its PR, they're more likely to buy again."

This was a concept especially useful during the recession, when fashion folks had to shift their designs and marketing from abstract to more commercial and pragmatic.

From there, the firm's budding relationships and referrals led to new business from up-and-coming designers, and word of BCPM's ability to nurture talent spread. The firm launched Derek Lam in the U.S. and later in London, initially advising him to infuse his collection with color to attract the buyers. It added Christian Lacroix after LVMH Moet Hennessy Louis Vuitton sold the brand.

"Two things Vanessa and I are known for in fashion is finding new talent and reenergizing old brands," said Ms. Phillips.

Now, the roster touts fashion clients Carolina Herrera and LVMH 's Edun, but the bulk of the firm's billings come from mainstream beauty brands and companies such as Starwood Luxury Collection Hotels and Resorts, Aldo, Rimowa and Richemont.

The pair acknowledges the relevance of digital in its clients' campaigns and in new-business meetings and has been working with a digital consultant on certain projects. Core to the evolution of the firm is the expansion of its lifestyle experience and finding new ways to support clients' businesses outside of PR, said Ms. Phillips.