‘The robes are polyester,” Anna Sui said, with a look of mock horror as she shrugged on a gown for a college graduation ceremony roughly four decades late.

It was in the early 1970s that Sui overheard two seniors in the lunchroom of Parsons School of Design mention an opening for a designer at Erika Elias’ neo-hippie fashion label Charlie’s Girls. Racing home, she threw together a portfolio, applied for the job and got it. Then, at 21, she promptly dropped out of school.

Instead of getting a diploma, she set off on a journey that saw her through four largely successful decades in fashion – a period during which she built a namesake label with 50 stores around the world, earned a lifetime achievement award from the Council of Fashion Designers of America and would find herself the subject of the first full-scale career retrospective of an American designer at a British museum, an event titled “The World Of Anna Sui” and accompanied by a coffee-table monograph with the same name.

Now, Sui was satisfying the long-held desire of her mother, Grace, by getting a college degree. Not just any degree: This was an honorary doctorate in fine arts, awarded by the Parsons School of Design at the New School before thousands of New School graduates and their families, all crowded in beneath the retractable roof of Arthur Ashe Stadium in Queens.

Outdoors, temperatures hovered in the unseasonal low 90s. Inside the stadium was a heat suggestive of the hinges of hell.

“I don’t know about this,” she said, looking dubious during a preceremony rehearsal. “There might be some people going down.”

Considering that since starting her label in 1991, Sui has worked with the world’s most celebrated models, from Kate Moss to Gigi Hadid, and has staged some of the more memorable shows in New York fashion history (to wit: Dave Navarro in a lace-trimmed camisole); and that she numbers among her close friends a sizeable percentage of the industry’s temperamental elite, she appeared surprisingly unfazed by it all – not the heat, the crowds or pressure of delivering suitably noble and uplifting commencement remarks.

She seemed, if anything, less humbled by a valedictory experience than curious about what there was to take away from it besides a scratchy polyester gown and an unflattering tasselled cap.

“My mother has been nagging me about this for years,” Sui said at a table in the tennis centre’s VIP area. Beside her sat her mother, two nieces and her brother Eddy. “She’d say, ‘When are you going to get your diploma?’. Well, look, Mommy, here I am.”

A constant in Sui’s life is her curiosity and quest for knowledge and novelty, said Bill Mullen, a seasoned fashion stylist who is a member of the designer’s inner circle.

“If you call Anna up and say, ‘Let’s go to this’ – it could be anything – and she’ll automatically say yes,” he said. “Her interests are so completely wide-ranging, it’s beyond. It could be some kind of mothbally, cobwebby old thing, or it could be some full-on nosebleed street culture helium thing and, either way, Anna’s there.”

In appraising Sui’s place in the landscape of American fashion, it is the array of interests and resources, books and movie references, images and songs she brings to bear that make her talent singular, said Andrew Bolton, the curator in charge of the Costume Institute at the Metropolitan Museum of Art.

“Anna has been consistent with her postmodern aesthetic right from the get-go,” Bolton said. “There’s not one art movement or artist she hasn’t touched on in her work, and I love being tested about unravelling those references, whether to Elsa Schiaparelli or the Duchess of Windsor or Kurt Cobain.”

There is perhaps something else. Like a number of those graduating that day from the New School, Sui is a first-generation American. A child of Chinese immigrants from Shanghai and Papeete, Tahiti, she was born in Detroit and raised in what she called “a Barbie doll suburb”. From the age of four, she was clear her career path would be as a fashion designer. And from her earliest years, she cast her eye on the wider world, the seemingly exotic one depicted in Life magazine.

Anna Sui has stood the test of time in the fickle world of fashion

In magpie fashion, she began amassing the shiny cultural oddments that would define her work as a designer. Every collection is replete with reference, whether to the English Mods or Hawaiiana or the hothouse orientalism of the Chinese-American film star Anna May Wong or Seattle grunge, said Dennis Nothdruft, curator of the Fashion and Textile Museum in London, where “The World Of Anna Sui”, which opened on May 26.

“It’s the fabrics, it’s the books, it’s the exhibitions, it’s the music” mashed up in Sui’s collections that render her a compelling designer, Nothdruft said. Although she may be inspired by something, he added, the results are seldom copy or pastiche. “She’s processing the information,” he said. “It’s not being processed for her. She loves things and knowing things and building the stories of things, into the clothes.”

As Sui said recently in T: The New York Times Style Magazine: “My brand evolved out of my lifestyle – the way I lived and the way I decorated my apartments.” That lifestyle could best be characterised as maximalist, since Sui acquires things with unparalleled gusto, as those who know her say, and is seldom happier than when working the aisles of a flea market or a souk.

“I saw Anna every Sunday for 20 years,” stylist Paul Cavaco said, referring to weekly visits to the 26th Street flea market in Chelsea. “I used to call myself Anna’s pack mule.” Among the categories of objects that have attracted Sui’s attention through the years are papier-mâché mannequin heads, linens by Vera, souvenir jackets, Japanese hankies, Army surplus jackets, qipao dresses, marabou bed jackets, wood-soled platforms from Goody Two-Shoes and Margaret Keane paintings of large-eyed waifs. Just as avidly as stuff, Sui has collected fascinating characters.

“Every time I go out for dinner with Anna, there’s always some surprise person I’ve never heard of before,” Mullen said. It may be a handsome violin virtuoso, a young K-pop star or the latest beauty to roll off the modelling assembly line.

“I remember coming onto the scene in the mid-90s, and Anna was already so established,” said Carolyn Murphy, long a modelling industry mainstay but in those days a neophyte. “She took me on as this country bumpkin, and it was like a rite of passage to be accepted into that circle,” of the superstars who formed a stable core of Sui’s runway coterie, people such as Naomi Campbell, Linda Evangelista, Kristen McMenamy and Christy Turlington.

“What was also great about it,” Murphy added, “was that unlike other designers doing the sort of usual American, sporty fashion then, here was a designer – Marc Jacobs was another – with a disruptive nature doing things that were whimsical, or grunge, or rock’n’roll.” If somehow that cool never translated into the magazine pictorials enjoyed by long-forgotten industry darlings, that was no deterrent.

“In a way it’s good that I had to find my own way,” Sui said. “I always tell students when I lecture not to follow well-worn paths, since they don’t really exist anymore, if they ever did.”

Though Sui’s designs are included in the Met’s permanent collection and would, as Bolton said, “have a big place” in any exhibition the museum might someday stage of American fashion, for the present anyone eager to experience her world of cowgirls, disco dollies, grunge girls, hippie chicks, hula girls, Mods, New Romantics, pirate molls, Pre-Raphaelite maidens and surfer nomads will have to cross the ocean.

And that makes a certain amount of sense, Marc Jacobs said.

“To me, Anna is a real designer and really, really knows fashion history, loves fashion, makes real fashion,” he said. “I don’t want to put anybody down, but New York fashion right now is such a bore.”