I am not in 23 Meteor Street, circa 1999. In fact, I’m in the BFI office in central London at the fag end of 2019. But by God, it’s easy to forget that, sitting opposite Nick Frost, Jessica Hynes and Simon Pegg, as they talk about their seminal sitcom Spaced, and each so jarringly reminiscent of their characters it verges on unnerving. Set on the fictional street in north London, Spaced told the deceptively simple story of two flatmates: aspiring-if-she-could-just-be-arsed writer Daisy Steiner and thwarted comic-book artist Tim Bisley. Accompanying them on their deeply prosaic adventures (a paintball tournament one week, a club night the next), which somehow achieved the heights of mythic glory, were their downstairs neighbour, tortured artist Brian (Mark Heap), his girlfriend Twist (Katy Carmichael), who worked “in fashion”, by which she meant a dry cleaners, Tim’s childhood friend Mike (Frost) and their landlady Marsha (Julia Deakin).

When the show aired, its meta humour, and jokes that were both silly and utterly brilliant, made cult stars of all the show’s major players, including its then-unknown director, Edgar Wright.

Today, Daisy-I-mean-Hynes, who as well as starring in the show co-wrote it with Pegg, fills the air with talk in galloping sentences that you have to cling on tight to in order to follow the logic. (“I didn’t want Daisy to be self-conscious, I wanted her to be spontaneous without angst. On the show Simon and I represent the middle, and Twist and Mike were more extreme, like the feminine and the masculine … ”) Meanwhile, Tim-I-mean-Pegg makes charming witticisms from the sofa and occasional light digs at his co-stars. (“None of us had done anything before Spaced. Well, except Jess, who was in [the little-loved 1993 Nazi big-band drama] Swing Kids, of course”; “Yeah, cheers for bringing that up.”)

And then there’s Frost, working his way through a bacon sandwich and maintaining a silent detachment. He is the first of the trio to arrive, whereupon he announces he knows neither what publication this interview is for nor what it’s supposed to be about. When I explain it’s for Spaced he immediately replies: “I don’t like talking about the past. But,” he says, with a head tilt towards Pegg and Hynes’s as-yet unoccupied seats, “they’ll absolutely love it.”

If he hadn’t long ago stopped playing Mike Watt – Spaced’s army enthusiast who tunes into a slightly different frequency from the rest of humanity – I’d assume Frost was an unlikely proponent of method acting. He only rouses himself when Hynes says she “still can’t just enjoy Buffy the Vampire Slayer”. “What’s your problem with it?” he says, as if squaring up for a fight. “We haven’t time for that now, OK?” Hynes replies, with an exaggerated eyeroll. Like I said, it’s hard to believe this isn’t Meteor Street.

Nick Frost, Simon Pegg and Jessica Stevenson with Mark Heap in Spaced.

This weekend, the cast will reunite for an all-day event as the show – somewhat shockingly – is turning 21 this year. This is less shocking for the cast who, as Hynes puts it, “have packed in quite a lot since then”. After making Spaced as unknown twentysomethings, Hynes – née Stevenson – became one of Britain’s best-loved TV stars, winning Baftas for her performances in W1A and There She Goes, while Pegg, who these days has the carved cheekbones of a man who hasn’t been near a carb in years, went on to endearingly improbable Hollywood glory, starring in Star Trek and alongside Tom Cruise in the Mission: Impossible franchise. He also made the Cornetto Trilogy – Shaun of the Dead, Hot Fuzz and The World’s End – which starred Frost and were co-written and directed by Wright.

Wright was an unknown 24-year-old when he directed Spaced. Today, he is so successful he genuinely doesn’t have time to come to the interview. Instead, I catch up with him on the phone the next day at an absurdly early hour, the only minutes he can spare these days between editing his latest film. Yet despite everything they have achieved since, they all – Frost excepted – love talking about Spaced. “I’ve worked since 1978, but Spaced is the most enjoyable thing I ever did,” Julia Deakin, who played the wise if often completely drunk Marsha, later tells me.

“It’s not every job where you get to hang out socially with the actors, but we all really did hang out,” Wright says. “It was that time before people had kids, so the show spilled into real life and back in a very nice way.”

Even the actors who were barely more than extras on it went on to become comedy stars. David Walliams, Mark Gatiss, Kevin Eldon, Peter Serafinowicz and Reece Shearsmith, all appeared, as did Ricky Gervais, who featured as a smarmy office worker called Dave.

“We’d seen the pilot for The Office before it was aired and we thought: ‘Shit, this guy’s gonna be huge, we have to get him for the show,’ says Pegg. “So we got him to basically play Brent for us. That was us being cynical.”

The Spaced house in Tufnell Park. Photograph: TMD properties

This Office/Spaced crossover now seems prescient: whereas The Office’s faux-documentary set-up made it the most influential show of the early 21st century in terms of format, Spaced coined the comedic tone for the next two decades in terms of style and writing. “I think I’d rather have that than it being just a format you can replicate in other territories,” says Pegg a bit pointedly. (Memories of a production company’s shortlived attempt to replicate Spaced in the US make Pegg and Hynes honk with laughter.)

All those absurdist film homages (Daisy spotting Mike’s gun in the kitchen, Pulp Fiction-style), all that playing with film and TV conventions (the slow-mo fights) and the mundanity of reality played against the grandeur of fantasy (Tim playing Resident Evil and suddenly his living room filling with zombies) have become part of the lexicon of modern comedy. Without Spaced, it’s hard to imagine Green Wing or Peep Show. “I love 30 Rock and Arrested Development and I sometimes think: ‘Ooh, those look quite Spaced-y!’” laughs Wright.

Just as Tarantino did in the movies a few years earlier, Spaced was the show that captured a new generation’s obsession with pop culture, playing with genre and self-referentiality. “It was supposed to look like how they would describe their lives to their friends: ‘I went to the DSS and it was like The Conversation,’” says Pegg. Not everyone got the references. “I had no idea what they were on about half the time!” laughs Deakin. “I’d think: Why am I saying ‘I love it when a plan comes together’ to a door? But it’s like Dad’s Army: even if you don’t entirely get what they’re talking about, funny is funny.”

Spaced was born from a reaction against how young people’s lives were depicted in the age of what Wright snickeringly refers to as “yoof TV.” “All the shows that were supposed to appeal to us, like Babes in the Wood and Game On, just had nothing to do with us, because they were written by older people,” says Pegg. “Channel 4 wanted something authentic.”

He and Hynes had met at an audition for a sketch show and clicked. They then met Wright while working on the brief-lived comedy Asylum, and the three were given free rein to create a primetime sitcom. Hynes and Pegg pillaged their own lives – even Tim’s nemesis, Duane Benzie (Serafinowicz), was based on someone who, Pegg swears, “had basically that name”.

“I also really wanted to create a show where there was equality,” says Hynes of her much-beloved character Daisy. “It’s extraordinary how few female characters have ambition and hold their own.” Even more groundbreakingly, Daisy’s gender neither defines her nor holds her back: her role on the show is neither to snog Tim nor act as the springboard for his jokes. She is just as funny, and game – and useless – as the men.

“It was a really big deal for me to be in the fight sequence with Simon, and also for it to not be a big deal,” Hynes agrees, referring to one of the most fondly remembered scenes on the show, when she and Pegg engage in a telepathic fight with a bunch of teenage boys.

“All the films I [wrote] with Edgar are very male and the female characters are ill-drawn and I think that’s because she’s not there,” says Pegg, referring to Hynes. “That’s not to denigrate the films, because I love them. But Spaced genuinely had dual appeal. Both characters appealed to both genders, and I think that was a revelation to some men.”

Clockwise from left: Jessica Hynes; Nick Frost; Edgar Wright; Simon Pegg, Photograph: Alicia Canter/The Guardian

Spaced ended after two perfect series and, despite fans’ pleas for a third, that was never possible: it was about a specific time in young people’s lives, and also a specific time in London. It’s unlikely two twentysomethings on the dole could live in such a massive place in Tufnell Park now; the actual house where they were supposed to live was on sale earlier this year for £3.25m.

“My best mate Danny bought it,” Frost pipes up. “Not because it was the Spaced house, he just liked it.” Is it weird going round there? “Oh I haven’t been,” he replies, Mike-ishly, and returns to his bacon sandwich.

“I feel like we really snuck in just under the line,” says Wright. “So much comedy now is relegated to the iPlayer or online. Even if Channel 4 were to make Spaced now, they certainly wouldn’t put it on at 9.30 on a Friday night.”

And the cast’s lives have moved on, too. While there is an easy banter between them, there are also a few tiny signs of strain, such as Pegg griping that Hynes refused to play the part he wrote for her in Shaun of the Dead. (“I didn’t want to play a character who dies!”; “She doesn’t die, she climbs up a tree!”) And Pegg and Frost, assumed to be best mates, barely interact during our time together. Well, time moves on. But Spaced has endured.

“When you watch Friends, there are some really shocking gender politics. But I don’t think Spaced feels dated like that,” says Pegg.

“Well, we did have the character of Vulva, ‘the big fat trannie’ [a gender non-specific performance artist played by David Walliams],” says Frost, quoting a line from Tim in the show, without looking up from his phone.

“Oh, Jesus Christ!” groans Hynes. All three of them become hysterical on the sofa, and for a moment it’s as if 21 years had never passed.

The Spaced 21st Anniversary celebration is at BFI Southbank, SE1, Sunday