There’s a lot to look at in Isaac Mizrahi’s studio in New York’s Greenwich Village: sketches, bulletin boards, fabrics, memorabilia, heaps of books, a Golden Girls puzzle set. But my eyes lock in on two dolls, Snoopy and his sister Belle (who knew!), clad in ballet-style tutus and embroidered vests. “I think I designed those,” he says, joining me from his apartment upstairs. “I love the Schultz estate and they like me a lot. It was a minute ago, though, so I’m not sure if they still even know who I am.” I later learn he created them for a 2014 exhibition at the New Museum, in an example of the symbiotic relationship with pop culture the designer has been nurturing since his childhood in Brooklyn. When we meet, he’s busy working on one of its other facets, firming up the setlist for Hooray!, his latest cabaret act in New York. It runs for four nights at 54 Below, a midtown venue, this month.

“I say it all the time,” he says of the cheery title. With his lit-from-within smile, you believe it. The slight twist is the source of that cheer. Mizrahi has held two New York residencies for the past decade or so – winter at the Carlyle hotel, summer at 54 Below – but he’s not a fan of the hotter season, finding July to be “just the nadir of the world”. The happy mood of his upcoming show derives from the knowledge that, come August, the summer’s almost over. Another reason for him to celebrate is the departure of World Cup crowds from the city, which will make it into his act’s version of Cole Porter’s You’re the Top that he updates every year. (He can’t immediately recall the lyric, but it rhymes “Spanish” with “mannish.”)

Primarily known as a fashion designer thanks to his vivid collections in the 80s and 90s and a slew of television projects that showcased his gregariousness (Time magazine called him “a kind of Seventh Avenue Oscar Wilde”), Mizrahi’s relationship to the stage goes back decades, and he’s been performing solo acts consistently since his off-Broadway debut at the nearby Greenwich House Theatre in 2000. Especially since scaling back his couture career, the 64-year-old says he’d like to also be known as a performer. “To think that I went to High School of Performing Arts before I was in fashion … ” he trails off, referencing his icon-incubating alma mater, memorialized in the film Fame. (He had a small part in the movie.) “I feel like I do this and I do clothes, which is crazy because the perception is not at all that. The perception is that I am a fashion designer.” But he believes his performances have sharpened and, over time, lowered raised eyebrows.

As Mizrahi’s designs blossomed into his eponymous fashion line in the late 80s, theatre never remained far away. He has fond memories of attending New York’s 2006 Sweeney Todd revival as Elaine Stritch’s date, and quotes the Broadway grande dame every few minutes. At one point, he pauses our conversation to straighten up three videotapes on his desk, which he plainly explains were sent by his close friend Stephen Sondheim. One is a VHS of Sondheim’s musical Evening Primrose, appropriately set at a department store. Stuffed into the sleeve is a typed note from the composer poking fun at Mizrahi for being on his way to owning his “Complete Works”. Sondheim’s reaction upon learning he hadn’t seen the rare TV production, he tells me, was a naughtily affected “Darling … ” It’s hard to imagine Sondheim camp it up like that, but in Mizrahi’s world, everyone is divine.

Mizrahi made his Broadway debut with a three-week stint in Chicago back in 2022, and I ask about his current theater-going diet. Perhaps my phrasing is unclear, or he simply picks up on that last word and runs with it. “Well, wait a minute, I started on a GLP-1 about five weeks ago, and I’m so thin already,” he beams. I follow his excited lead. “I had a suit made over Covid,” he goes on, “this kind of silvery, lamé suit that I had made for my first residency back at 54 Below – and it never fit.” He’s giddy to finally break the outfit out of the bag in which it’s been resting.

Having read his 2019 memoir (the perfectly titled I.M.), I know that body image has long been a concern for Mizrahi. With the weight-loss drug boom some five years behind us, why the wait? “I’d been waiting to see if everyone grows, like, an arm,” he deadpans. “I mean it! Also, the more I try to diet, the more I go crazy and don’t diet, so I keep putting weight on that way.” What about the required maintenance? “I’m fine with that if I reach some kind of goal. I have some pants hanging over there that I got out of storage, and if I can get back in those, darling, I will never eat again.”

I repeat my original question. “Oh, I try to see every show. I try to see every damn thing.”

Next month, a 4K restoration of Mizrahi’s 1995 film Unzipped will open in the US, injecting the glamour of the peak supermodel years into our corporate Shein landscape. A terrific document of process, fashion and personality, the Sundance winner charts his 1994 fall collection from inception to runway, with a cavalcade of cameos from Naomi Campbell and Eartha Kitt to Kate Moss and Liza Minnelli, each fabulously in step with the designer’s wit and style. With textured black-and-white photography and backstage footage of legends bopping about to house music, it is a perfect capsule of 90s chic – both the final gasp of unreachable 20th century celebrity and the first breath of all-access relatability.

Despite its success, it fell into something of a copyright purgatory and went largely unavailable, lending a coveted aura to the DVD bootlegs and files that circulated. The film was directed by his then-partner Douglas Keeve, evincing a vulnerability from its subject that he didn’t sense during the shoot “because it was my boyfriend just rolling tapes, taking this footage”. (“Why would you show me this? It’s like you get some cruel pleasure out of it,” Mizrahi cries in a scene where an employee reveals that Jean-Paul Gaultier’s latest line beat him to the same source of inspiration.)

Whereas early watches would prompt self-critical reactions about his weight or appearance, he says the viewing experience now is far sweeter, and more nostalgic: “Look how thin and cute you look.” Working to secure the rights for re-release became a project of posterity, “simply because it’s a big landmark in my life and a big part of what I think of as my legacy”.

Mizrahi had established himself as a mega-watt talent by the time of the documentary’s filming in 1994, with his eponymous label bankrolled by Chanel starting two years before. But the no-holds-barred access we’ve come to expect in the era of reality TV, not to mention the toting around of film equipment “was so uncomfortable and gauche”, he says, looking aghast. “In Paris? Oh my god, to have a camera crew following you with John Galliano and André [Leon] Talley was mortifying.” What drove him was a genuine love for the world he’d created for himself, which he didn’t often encounter elsewhere in the fashion world: “I just thought, ‘My fittings are hilarious, someone has got to get this.’

“That was, for me, the best part of the movie, talking to Christy [Turlington] or Shalom [Harlow] in a fitting room,” Mizrahi continues. “So I was ready to bear the rest of it based on how much I love the idea of someone capturing this for posterity.”

While a student at Parsons School of Design, he worked part-time for New York designer Perry Ellis. “It was the greatest thing in the world, because he was very funny,” he says. “All the people in the studio were hilarious, and when they liked something, they would say, ‘Oh my god, this is hilarious.’ That’s how they would describe a beautiful dress.” That “slightly whimsical, never boring” atmosphere embedded itself into Mizrahi, who kept a light atmosphere at his label, which closed in 1998. “I feel like if I followed in anybody’s footsteps, it was in Perry Ellis’ footsteps. Not if,” he corrects himself. “Yes, I did, and I took it one step further and really tried to be very funny.”

What excites him most about Unzipped’s re-release is the chance to revisit what he views as a bygone era. “In those days, fashion was a scene, and now it’s a scene but in a different way,” he says. “It’s a very corporate thing where you pay people to come to your show; you have a lot of control over it. In those days it was completely out of control.” Thousands of people crammed into tiny spaces, fire department be damned, and sometimes, as in spring 1992, the power would simply go out mid-show. But, he rhapsodizes, “it was great, and all of a sudden Madonna would come, or Robert De Niro or Prince”.

That scene he reckons as coming to a close sometime between 2000 and 2010. Growing up idolizing Jackie Kennedy Onassis and Mary Tyler Moore – the women who influenced his ultimate icon, his mother – he takes a beat to consider who inherited the trendsetting baton. The Olsen twins and Sarah Jessica Parker, for a while. Now he thinks it might be the Kardashians (“just the shape of those women, the shapes that they took”) or the Real Housewives: “Say what you want about them, but they are pretty influential in terms of how they push things. They don’t look great all the time, but they push it, darling, they push it.” What’s still missing for him is what he calls “aspirational style”, which “came down from the mountain” through couturiers such as Dior, Balenciaga and Norell – “these gods”, he says. “It was always that influence, that high kind of style that would then get fitted onto Jackie, and then you got Mary Tyler Moore looking like the real man’s version.”

He’s not funereal about this. Rather, he understands his role in the change of tides. Yes, the top-down transmission of fashion is gone, with “no real spine” anymore. But now, he says, “it’s just everywhere – which I love. That’s one of the things I was pushing for when I was working; you could show a skirt that’s this long and then one that’s this long on the same runway. I did it because I thought that is where we’re going. That is the way I want to dress.”

After the cabaret wraps and Unzipped makes its way back into theaters, his hopes will be focused on a TV series in which he has a part getting a green light. He is tight-lipped about the project, which he says is already written, other than to offer love for its undisclosed director. “We’ll see if it gets made, we see a lot of things,” Mizrahi acknowledges, before closing with words that offer a possible explanation for his own continuing success. “I’m unaware of how everything happens, but I’m sure glad that it’s happened.”

• Isaac Mizrahi’s Hooray! is at 54 Below, New York, from 12-15 August. Unzipped is re-released in US theaters on 25 September with UK and Australia releases to follow