At Louis Vuitton’s fall 2015 runway show in Paris, the 29th look featured a romantic sweater. Its sleeves—narrow at the wrist—blossomed up and out at the shoulder. Designer Nicolas Ghesquière experimented with that new sleeve in look after look, including the silvery dress that closed the show on supermodel Liya Kebede.
Reviewing the fall collections two weeks later, some faculty members at the school of fashion at the influential Savannah College of Art and Design noted that Marc Jacobs and Miu Miu had shown a similar sleeve, often called a mutton sleeve, but its presence on Mr. Ghesquière’s runway suggested an important new trend. “Nicolas added the exclamation point on that silhouette development,” says Michael Fink, dean of SCAD’s fashion school.
Is mutton the shape of sleeves to come? It isn’t clear yet. But Mr. Ghesquière is one of a small cadre of designers whose whims on the runway sometimes go nuclear, setting trends and even creating new classics. In his previous job at Balenciaga, he ignited fascinations with gladiator sandals, futuristic scuba-type fabrics, and $1,000 cargo pants.
Studied by retailers, academics and fashion lovers alike, designers like Mr. Ghesquière have an uncanny connection with the broader culture, the courage to put forth concepts that may be roundly criticized—and an obsession with doing something completely different.
“These are people who are real neophiliacs,” says Valerie Steele, fashion historian and director of the museum at New York’s Fashion Institute of Technology. “They love something new.”
When designer Phoebe Philo put fur-lined Birkenstocks on Céline’s spring 2013 runway, fashion had suffered through years of the biggest, highest, clunkiest platform heels imaginable. Even fashionistas, it turned out, were ready for a change.
Often, the look initially seems jarring or ugly. I laughed out loud in Paris at that Céline show and was sure those Birkenstocks, however delightful, would never take off. By the following season, front rows were rife with white two-strap Birkenstocks. Birk-style sandals have since been done by labels at every price, and the trend has evolved: The chicest feet now tread in hiking boots and Nike running shoes. One can find the seeds of “norm core”—the embrace of suburban attire like dad jeans and white sneakers—on Ms. Philo’s runway.
“There’s a moment of pause— and then it just goes ka-boom!” says Julie Gilhart, a fashion consultant who once was charged with sniffing out these gonna-explode fashions as the fashion director of Barneys New York.
Sometimes, designers can create whole new product categories. Ms. Gilhart cites the moment in 2003 when Alber Elbaz showed tulle-covered costume jewelry for Lanvin. Almost overnight, labels that had left jewelry to the jewelry brands started producing bracelets, necklaces and earrings—and consumers gobbled them up. “That started designer jewelry,” she says. Mr. Elbaz is also largely responsible for the ballet-flat phenomenon. He wasn’t the first to do them, but Lanvin’s flats became covetable and established the trend.
And those Ghesquière cargo pants at Balenciaga in 2002: “They were $1,000—for cargo pants!” Ms. Gilhart says. “And then they just took off.”
Often, influential looks are at first criticized by fashion insiders. Many editors sneered at Hedi Slimane’s debut collection for Saint Laurent for spring 2013, griping that the floppy hats and swishy dresses failed to do justice to the tailored label. Soon, though, his broad-brimmed hats—and many copycats—were on streets all over the globe, and the Saint Laurent brand was reborn almost overnight—doubling its revenue last year.
Influential designers don’t always get the immediate, direct benefit of their creations, though it later builds great careers. Marc Jacobs was fired for his 1992 grunge collection at Perry Ellis. That was the moment the Seattle-music-scene grunge look went mainstream (leaving Kurt Cobain to don a “Grunge Is Dead” T-shirt).
Vivienne Westwood reintroduced corsets and an ultrafeminine silhouette in dresses with her 1985 “Mini-Crini” collection, but Ms. Steele notes that it wasn’t until Christian Lacroix did his own versions two years later that the look took off.
Some influential runway collections are so unwearable that they can only become collectors’ items—but they influence other designers to think differently. Rei Kawakubo’s 1997 “Lumps and Bumps” collection for Comme des Garçons, which placed irregular bulges on models’ bodies, was laughed at as “Quasimodo clothes,” says Ms. Steele. But it led other designers to be freer with volume, allowing fabric to flow in new ways.
What are they thinking when they come up with these ideas? Mr. Ghesquière introduced mutton sleeves—originally named for a shape resembling a leg of lamb—after many seasons in which fashion has been dominated by narrow, tailored sleeves. Mr. Ghesquière declined to comment.
Ms. Westwood said her Mini-Crini collection in 1985 was an attempt to kill the 1980s masculine big shoulders. More often, though, designers struggle to articulate the source of their concepts. Designers often fall back on citing a vacation, a painting, or a piece of architecture—ideas too general to explain how they arrive at the shape of a pocket or of a sleeve.
Ms. Steele says most designers are just going with what they like at the moment. “Designers are visual people,” she says. “They work intuitively.”