As Friends wrapped up its fourth season in May of 1998, Ross and Rachel’s on/off relationship still provided the show’s emotional core, with the other four roommates serving as the platonic Greek chorus to the couple’s climactic kisses and “on-a-break”-dom. But then, in the second half of the season’s hour-long finale — the one with Ross’s ill-fated London wedding weekend with Emily — another duo surprisingly hooked up, much to the glee of audience members: Monica and Chandler. Their relationship would evolve as the complete opposite of Ross and Rachel’s: long-kept secret from the other roommates, and healthy and strong until the series ended with them married, parents of adopted twins. Although pairing off sitcom characters is always a risky venture, especially when a show already has one successful couple, Monica and Chandler quickly became a fan-favorite romance, with viewers loving the chemistry between Courteney Cox and Matthew Perry. Back in 2013, when this story was first published, former Friends exec producer Scott Silveri, who co-wrote the episode with future wife Shana Goldberg-Meehan (and, as with most sitcoms, lots of input from the rest of the show’s writing staff) explained the genesis of the relationship, the reservations that nearly stopped it from happening, and why he thinks it added years to the show’s life.

Friends was nearly 100 episodes into its run before the show’s writers played the Monica-and-Chandler card, but the coupling was something that almost happened earlier. The idea had been “kicking around” since before Silveri and Goldberg-Meehan joined the show in season three, he remembers, with his predecessors taking note of the chemistry between the two characters as early as the season-two episode “The One Where Ross Finds Out.” That plot had Monica acting as a trainer for Chandler as he tried to shed a few excess pounds, and “there was a real fun dynamic between the two of them,” Silveri says. “So even as early as that, they said, ‘Oh, they’re kind of special together. If we’re ever looking for another relationship, that’s something to file away.’”

The notion of Monica and Chandler was also seriously pitched in the writers’ room in season three, Silveri says. “People got excited about the idea,” he says, including himself among that group. Goldberg-Meehan, however, thought it was simply too soon in the show’s life to introduce another couple. “She was the one who said, ‘I just feel like at this point it would feel a little desperate,’” Silveri recalls. “We had gotten excited about the stories we could tell, but once she said that, we were all shamed and ran away. It became clear it was too early to explore something like that.” Another reason the writers put a pin in the idea: “There was a little bit of relationship ennui among us writers,” Silveri says. “We’d already done a lot of drama between Ross and Rachel. And nobody wanted it to become the ‘Get Together and Break-up’ show.”

But after season three, with Ross and Rachel well into their legendary “break,” the timing objections started to melt away. “We weren’t so immersed in relationships,” Silveri says. Plus, the logic of another coupling was starting to grow stronger, at least in the eyes of some of the writers. “The thinking was, if the show’s going to be entertaining for years to come, it can’t simply rest on this one [Ross and Rachel] relationship,” Silveri says. “So it follows that if another pair got together, that would be fun and provide more story. And it’s organic: If you get six friends together, all around the same age, there’s gonna be a little mixing and matching as time goes on. It felt real.” As they got together in summer of 1997 to map out story lines for the upcoming season four, the writers decided that bringing Monica and Chandler together would be, according to Silveri, “a great goal for the end of the season.” They just needed to figure out how.

The writers knew they couldn’t “do the exact same thing” as Ross and Rachel, Silveri explains. Their different approach mirrored how people often approach new romantic relationships, “which are often reactions to the last relationship you had,” he says. “If someone’s too high drama, you look for someone stable. And so with Monica and Chandler, we decided to roll out in a way that was a reaction to the last big relationship [the show] had.” Specifically, they wanted to keep things low-key. “With Ross and Rachel, it was so public, it was experienced by the group,” Silveri says. “Like, before there even was a ‘Ross and Rachel,’ there were the guys coaching Ross [about how to get her]. And then in the third season, with the breakup, it affected the six of them as much of the two of them. We’d ridden that bus as far as we cared to.” So the mandate was to introduce Monica/Chandler in a way that “would be not too heavy, not too soap opera, but also something surprising.”

What the writers came up with was definitely a shocker. Yes, some Friends fans probably saw hints of a relationship coming for a while; the first episode of season four had the twosome cutely bonding over a jellyfish sting. But it’s hard to imagine even the most ardent ‘shippers expecting the big reveal to happen during the wedding, when there was so much focus on about Rachel’s emotions about Ross marrying someone else. The hookup happened suddenly in the last half of the show, with zero preamble; after Ross excitedly bursts into Chandler’s hotel room then leaves, Monica pops out from under the covers and asks, “Do you think he knew I was here?” to much audience shrieking. (A season-seven episode, “The One With the Truth About London,” revealed more details.)

“The goal from the get-go was to treat Monica and Chandler’s hookup as a surprise, a jolt in the second half of the hour-long episode to add some energy and fun,” Silveri says. “The only real debate was around just how we’d get Monica and Chandler there that morning, how many crumbs to drop to lead the audience and the characters to the moment, all in hopes that the fact that they ended up in bed that morning wouldn’t feel unmotivated and false.” In earlier scenes at the rehearsal dinner, Chandler had tried to talk a drunk Monica out of her funk over having no boyfriend, and a drunk party guest mistaking her for Ross’ mother. “Who wouldn’t want you?” he asked. Says Silveri, “[We were] basically shooting for the spot between, ‘This stinks, that never would have happened!’ and, ‘This stinks, I saw that coming!’ More of a delighted, ‘That is surprising, but also very satisfying and organic. It might not stink!’”

Silveri and the other producers got a sense of how viewers would react to their storytelling decisions months before the episode aired on NBC. With the episode shooting in London (where the show was also a hit) instead of Burbank, producers wanted to give as many locals the chance to see a taping as possible. So rather than following the standard practice of filming multiple takes of scenes, producers instead shot the episode all the way through, like a play, for three different studio audiences. “So we got to experience them seeing that [Monica and Chandler] scene three times,” Silveri says. “The first time, I was huddled around a monitor, watching [the actors] perform. And when Monica popped up from beneath the sheets, there was just this explosion from the audience. It was a combination of a laugh/gasp/cry/shriek. They were just blown away by it. It was so intense, for the second or third takes, instead of watching the monitors, I just turned around and watched the audience.” Today, of course, producers would’ve filmed that scene on a closed set, fearful that audience members would tweet about the moment the second they left the studio. “Before the dawn of social media, you could keep secrets,” Silveri laughs. “We didn’t have to worry about it.”

But while in retrospect it all seemed like the perfect beginning to what would become a great TV relationship, Silveri insists that while he and Goldberg-Meehan wrote the London episode, they weren’t sure the whole thing would last. Even later that year, when the writers returned from hiatus and began breaking stories for season five, “The question was, ‘All right, is this something we dispense with after a week? [or] Is it something we explore a little more?’,” he says. In fact, Silveri admits the London hookup was something of a trial balloon, designed to see how viewers reacted to the idea, and if Perry and Cox had the sort of sexual chemistry that producers thought they might. Co-creators Marta Kauffman and David Crane were always “eager to try things” on Friends, says Silveri, but they also always tried to make sure they didn’t get stuck in boxes they couldn’t get out of if need be. “They did that with all of the relationship arcs,” Silveri explains. “With Courteney and Tom Selleck [in season two], if I’m not mistaken, there was no sense [at first] that was going to become a relationship with a capital ‘R,’” he says. “They went into that, and it was going to be one episode, two tops. And then they had such good chemistry, the producers and the writers at the time decided to explore it a little more.” So with Monica and Chandler, “There were plans, but there was no [final] decision,” he says. “It was always, ‘We’re gonna see how it feels … We’re gonna see how it plays to the audience,’ and then go forward from there. It was sound producing on their part.”

The take-it-slow approach also helped smooth out another potential pitfall of Monica-Chandler: the actors. The writers knew Perry and Cox, along with the other four series regulars, were protective of their alter egos, particularly when it came to romantic entanglements within the group. “I’m remembering there were a lot of conversations about, ‘Is this the right thing to do?’,” Silveri says. “I don’t think anybody balked too much at them hooking up. That felt natural. The fallout came in the following year, when it became a relationship. They were acutely sensitive to how it played out.” That hesitation, plus the writers’ own doubts, helped shaped the first half of season five. “We plotted it out in a self-protective way,” he says. “It wasn’t a relationship [the other characters were] talking about. Nobody knew about it. We as writers were almost as protective of it as those characters were. We didn’t want to make too much of a deal about it too early. That’s what you saw on the screen, but it’s also how we experienced it. We didn’t want to spend too much too fast. We didn’t want it to be high drama. So we just kept taking baby steps forward and feeling our way through.” And it seemed to work: Audiences embraced the two as a couple, and Perry and Cox ultimately accepted the idea as well. “Because of the way we eased into it, we sort of greased the machine,” Silveri says.

In the end, the pairing of Monica and Chandler ended up rivaling that of the show’s core romance, Ross and Rachel. It altered the show’s dynamic, but didn’t ruin it. This was no small feat: Most shows have trouble managing one big couple (see: New Girl), let alone two. And even Friends didn’t make every coupling click: Joey and Rachel flirted with a relationship toward the end of the show’s run, but the two didn’t go all the way. (“They ultimately did feel more like a brother/sister relationship,” Silveri says.) Monica and Chandler, however, just worked — and Silveri believes that success was a critical component to the show’s ultimate longevity. “If you didn’t have a Monica-and-Chandler relationship, if the center of Friends had remained Ross and Rachel, you would’ve seen a much shorter shelf life for the show,” he says. “Without Monica and Chandler, it ends three years earlier. I don’t owe my whole house to them, but at least two bedrooms and a bath are because of them.”

How Friends Decided to Pair Off Monica and Chandler