NEW YORK >> In a surprise finale to his Fashion Week show, Alexander Wang sent an army of 70 models down the runway to announce his new collaboration with adidas Originals. Christian Siriano was inspired by the casual chic of Capri and earned applause for a few plus-size models who walked his runway, and Banana Republic presented looks influenced by India as New York Fashion Week continued Saturday.

Some highlights:

———

A SURPRISE FINALE — AND NEW PARTNERSHIP — AT ALEXANDER WANG

Alexander Wang is, by his own description, a total sneakerhead. He once even designed a whole clothing collection around them, with dresses, tops and handbags emulating his favorite sneaks, like the classic white-and-green Adidas Stan Smith.

Now, Wang has taken his sneaker love to a new level, partnering with adidas Originals for a line of apparel and footwear that seeks, in his words, to “disrupt” the famous Adidas look while still preserving its familiarity. One example: rotating the well-known trefoil logo upside down. Another: “deconstructing” the Adidas sneaker. Also, the entire collection is unisex: Tops, bottoms, shoes.

Wang introduced the new line as a surprise finale to his Fashion Week runway show Saturday night, in a huge space on a Hudson River pier. After modeling creations from Wang’s own label, models rushed backstage to change into new Adidas garb, while a one-and-a-half minute film teased the new collection.

Then they marched onto the runway, more than 70 of them, all clad in black, as the crowd — which included Madonna and Nicki Minaj — craned their necks and snapped endless photos. It was, Wang said, “the biggest show we’ve ever done.”

In designing the new line, the key challenge was to change up the Adidas look so it feels fresh — but not to the point that it’s unrecognizable, Wang said in an interview.

“It was really about saying, how do we take something and shake it up a little, disrupt it, but at the same time not change it so much where it doesn’t feel right.”

The 32-year-old designer is recognized as one of the most talented and busiest of his generation. He launched his own, eponymous label 11 years ago, at age 21. Last year, he ended a prestigious three-year stint as creative director at Balenciaga, a job that had him splitting his time between Paris and New York. Since then, he’s been back fulltime at his own label, where he focuses heavily on streetwear — and is a favorite of the celebrity set.

As for Adidas, it clearly wanted to capitalize on Wang’s edgy and youthful vibe.

“I’ve been a fan for a long time, this connection he has with culture and New York and breaking down boundaries,” said Nic Galway, vice president of design for adidas Originals.

For Wang, it was a chance to work with a brand he often wore as a child, and especially to work with sneakers.

“I grew up on sneakers,” he said. “It’s a very interesting time obviously for (all) sportswear, the whole market and how people utilize fitness, incorporate it into their daily uniform. So the sneaker is something that I’ve always been very close to. And it’s always been something that’s very hard for us to do in house, to be honest — obviously Adidas has the most innovative resources.”

Wang also showed his own label’s spring collection on Saturday night, and it was a marked contrast to the all-black garb that came later: Colorful, whimsical warm-weather clothes that seemed destined for the beach.

The designer said backstage that he was going for a “liberating, free, surfer attitude and sensibility. Everything was put through the lens of water sports.”

Wang’s after-parties are as famous as his shows. As guests left the runway, they walked into a cavernous space filled with colorful trucks, some dispensing snacks, Slurpees, or stronger beverages. Partiers could even take a can of spray paint and decorate a van, if they chose.

—Jocelyn Noveck

———

SIRIANO MAKES A STATEMENT ON SIZE

Five models who were NOT sample size got a few cheers from the crowd as they walked the beachy, Capri-themed runway of Christian Siriano.

Siriano’s strong statement on size comes after 6-foot tall Leslie Jones complained in July that no designers wanted to dress her for the “Ghostbusters” premiere. Siriano made her a red gown, and he dressed the curvy Uzo Aduba in the same color Friday night at the Toronto Film Festival screening of her “American Pastoral.”

On Thursday, “Project Runway” mentor Tim Gunn wrote a thought-provoking takedown of most top designers for ignoring plus-size women, considering — as he wrote in The Washington Post editorial — that research shows the average woman in the U.S. wears size 16 to 18.

“I’ve dressed so many different types of women and it’s fun,” said Siriano, who won the fourth season of “Project Runway” back in 2008. “I grew up with a mom who was a 16 and a sister who was a zero. There should be normalcy, I think.”

Among those applauding the models of size was Ashley Graham, who made history as the first plus-size model to hit the cover of the Sports Illustrated Swimsuit Issue this year.

To be sure, plenty of Siriano’s walkers were the usual model thin.

It’s been a big year in other ways for Siriano, who got hitched to longtime boyfriend Brad Walsh at their country home outside New York City over the summer. Soon after, on July 25, first lady Michelle Obama appeared in a royal blue Siriano dress that fell just below the knee as she addressed the Democratic National Convention.

“It was an amazing, amazing moment,” Siriano said backstage before his show of ladylike, Capri-inspired looks. “Every now and then it’s nice to have someone like that just give you a little bit of a push that you need for the world to agree.”

—Leanne Italie and Gina Abdy

———

BANANA REPUBLIC GOES TO INDIA

Gap Inc.’s Banana Republic brand offered a presentation of 40 spring looks for men and women, inspired by its design team’s trip to India early this year.

“We were loving the idea of the old meeting the new, like technology meeting the old handcrafted ideas,” said Michael Anderson, senior vice president of design for the brand. “Everybody does a lot of manufacturing in India, but we wanted to show a different side to India.”

In particular, the design team was inspired by the lattice work in that country, using a vendor in Portugal to do laser cutting of fabrics.

For women, there were off-the-shoulder laser cut eyelet tops paired with matching skirts, shirt dresses styled with white trousers and pajama-styled striped shirts and matching pants. For men, there were plenty of fashions in madras plaid, including shirts, pants and vests. The collection highlighted colors that included oranges and cinnamons.

For those who can’t wait until next spring, Banana Republic offered 15 looks from the women’s collection that can be purchased on its website now or at Banana Republic’s store in New York’s Flatiron district. That capsule included a one-shoulder asymmetric dress in red stripes and a cream-colored, laser-cut blouse. It’s the second time the brand made some pieces available for purchase right away.

“We want to have a deeper relationship with our consumer,” Anderson said. “There is a customer who is on the edge. They want things before everybody else gets them. There’s this heightened sense of urgency.”

—Anne D’Innocenzio