What would Karl have thought? Watching the stream of Lagerfeld-a-likes mount the steps of the Met Monday night in their black and white, it was hard not to wonder.

Yes, the evening’s dress code dictated “in honor of Karl,” the evening itself in honor of the opening of the Costume Institute exhibition dedicated to the designer’s work. Yes, Mr. Lagerfeld had made himself into a caricature, with his uniform of black jeans, high white-collared shirt, black jacket, fingerless gloves, black silk cravats and black shades. And yes, the gala itself often feels like high-fashion cosplay, with guests trying to outdo one another in the attention-getting sweepstakes.

But Mr. Lagerfeld, who attended the party seven times and was a co-host once, in 2005 when the subject was Chanel, was also a man who had no truck with looking back, and who once announced, “I don’t want to see all those old dresses” when asked about an earlier retrospective of his work. And this was a gala full of old dresses. (A positive change, for once, from all the one-offs of the past.)

Vintage was everywhere: a mint green Chanel from 1988 on Penélope Cruz, a co-host, and a white Chanel princess dress from 1992 on Dua Lipa, another co-host; a corseted 1993 Chanel on Margot Robbie and a pink and silver 2010 Chanel column dress on Naomi Campbell; even Nicole Kidman reprising the feathered Chanel she wore in a 2004 ad campaign for the brand. Also old Chloé: a remade violin dress, originally designed by Mr. Lagerfeld in 1983, on Olivia Wilde and a remade shower dress from the same collection, revived for Vanessa Kirby.

And Fendi, courtesy of Lila Moss Hack in 2018 couture — “vintage” being a fungible term these days — and Suki Waterhouse in a floral dress from the spring 2019 collection. (Watching the red carpet felt a bit like a treasure hunt through fashion history: Guess the season!) That’s recycling for ya.

What was striking was how good all of it looked. In some ways, dedicating the evening’s dress code to Mr. Lagerfeld was an opportunity for a reset, an opening for attendees to eschew the temptation to the ridiculous and embrace a return to elegance.

The designer did, after all, believe in making an effort. (He once derided sweatpants as “a sign of defeat.”) And a lot of guests did. In comparison to recent galas such as “Camp” and “Heavenly Bodies,” the kitsch element was notably understated.

There were some obvious exceptions, of course, most notably the Choupette avatars: Jared Leto, in full white Birman costume (he later changed into a black suit and cape); Doja Cat in a pearl-and-feathered Oscar de la Renta cat gown and facial prosthetics; Lil Nas X in pearl-covered silver body art and G-string.

But compared with the plethora of calmer bouclés — even the striptease by Janelle Monáe in an enormous Thom Browne tweed coat on a pyramid-shaped superstructure that was peeled off by a set of helpers to reveal a sequined bikini, and Anne Hathaway’s safety pinned Versace-does-tweed — they looked a little desperate. (To be fair, Mr. Lagerfeld, who once built a supermarket in the Grand Palais, appreciated a viral statement as much as anyone and probably would have been amused.)

Even Kim Kardashian, in ropes of Schiaparelli pearls at her neck and waist atop a flesh-toned corset, seemed out of place, as if she was trying too hard. This despite the fact that the pearls were a clear reference to Mr. Lagerfeld’s Chanel, and his fashion-changing facility with a brand signature, and showed up again and again in more toned-down looks on other guests. See, for example, Lizzo’s black pearl-strung Chanel and the ropes of nacre around Taika Waititi’s gray silk Prabal Gurung tuxedo coat.

Indeed, the carpet was full of not-so-hidden Lagerfeld references, like the high collar of Julia Garner’s white satin Gucci halter-neck gown and Cardi B’s black patent leather camellia-festooned frock from Chen Peng Studio, which came with its own shirt and tie. Not to mention the gloves, shades and tie pin worn by Ke Huy Quan in Dior Men; the white trompe l’oeil shirt and tie of Stephanie Hsu’s sequined Valentino gown; and the “Choupette blue” of James Corden’s Brioni tux (so-named by Mr. Lagerfeld in honor of his cat’s eyes).

Then there was the quilted handbag carried by Olivier Rousteing of Balmain, with “Karl Who?” scrawled on the side. It was a nod to a tote bag once carried by the designer, who had a relatively healthy sense of humor about his own absurdity. Mr. Lagerfeld probably would have appreciated the stair-sweeping cape Mr. Rousteing designed for Jeremy Pope with an enormous Lagerfeld likeness at the hem. He did, after all, put his face on a T-shirt for H&M for their collaboration. He liked the idea of being an apparition.

Still, of all the Lagerfeld gestures on view, perhaps none was more genuinely Lagerfeldian than Rihanna’s arrival just after 10 p.m., a point in the evening when some guests were already leaving the party. In her camellia-covered Valentino cocoon and white baby-bump-embracing gown, she swept in on the arm of ASAP Rocky, who was himself wearing Gucci jeans and kilt à la an outfit worn by Mr. Lagerfeld for a runway bow at a 2004 Chanel show. Mr. Lagerfeld was, of course, perennially late for everything. Often by hours.

He, of all people, would have applauded the entrance.