NEW YORK, United States — Gigi Hadid walked the runway at Victoria's Secret's annual fashion show for the first time this year. A popular model and friend of Kendall Jenner and the Kardashian clan, the 20-year-old was clad in flashy yellow firefighter pants and clutching a toy Dalmation as teen idol Selena Gomez performed. The entire production, bright and vibrant with a towering balloon structure looming over everyone, was orchestrated to appeal to a younger set than the rest of the show.Hadid wore Pink, Victoria's Secret smaller sub-brand, which has had its own devoted segment at the much-hyped special for the past 10 years. Lately it's become an increasingly key part of Victoria's Secret overall business, serving as both a standalone franchise and a way to get shoppers into the main label when they're older."Pink is very important to the business," said Simeon Siegel, an analyst at Nomura Securities. "It effectively welcomes customers into the Victoria's Secret family before they would shop at Victoria's Secret."Victoria's Secret introduced Pink in 2002 as a way to attract high school and college girls. Unlike the main label, Pink is more loungewear than sexy lingerie. Thong waistbands are wrapped in the Pink name, and holiday bikini panties sport lines like "#ELFIE" and "Santa Stop Judging Me." The website boasts a whole section for dorms, filled with such home goods as blankets, storage bins, and laundry hampers. There's also a whole line of pajamas. “When somebody’s 15 or 16 years old, what do they want to be?” Stuart Burgdoerfer, chief financial officer at parent company L Brands, asked at a conference in 2013. “They want to be older, and they want to be cool like the girl in college, and that’s part of the magic of what we do at Pink.”Victoria's Secret has amped up its devotion to Pink of late, opening more stores and pumping investment into its bra business. Although L Brands doesn't break out sales figures for Pink, executives repeatedly cited Pink as a sales growth driver over the past year and said the brand has more than doubled its sales over the past five years. In May, Victoria's Secret Chief Executive Sharen Jester Turney said Pink continues to "perform on all cylinders."It's a crucial piece of Victoria's Secret's expansion. In 2010, Victoria's Secret opened its first standalone Pink store and has been expanding the brand ever since. Now, 137 Pink shops crisscross North America and the U.K. The retailer wants to open Pink stores side by side with the mainline shops anywhere it can. Martin Waters, who runs L Brands's international business, hinted at overseas plans for Pink at the company's investor day in November. "Over time, could we imagine even more Pinks than Victoria's?" said Waters. "Maybe.""Pink is really quite core to square-footage growth," said Bridget Weishaar, an analyst at Morningstar. "It is a very, very pertinent component of their growth story."The annual fashion show is another big marketing play for Victoria's Secret, which counts on the event to build hype through the holiday season. Dropping names such as Hadid and Gomez into the Pink fray is a clever way to court the teen market. Still, Pink's marketing has come under scrutiny over the years—after all, it's selling intimates to teens and college kids. Outraged parents took on Victoria's Secret in 2013 over Pink's "Bright Young Things" slogan, slamming the company for sexualizing girls. Victoria's Secret said the line was meant for college spring breakers.Hadid and her fellow models who walked in Tuesday's Pink segment were, per usual, in less sexually overt outfits than they were in the rest of the show. In one of the non-Pink parts, Hadid donned a much more revealing set of turquoise lingerie, decked out in butterfly wings.By Kim Bhasin, Lindsey Rupp; editor: Katie Drummond.