Out Of Every Plot Twist On Friends, This One Stands Above The Rest

"Friends," the 1994-2004 sitcom created by David Crane and Marta Kauffman, is just as relevant today as it was while it was on the air. Its popularity has remained so strong that a reunion special recently aired on HBO Max, in which the cast and creators discussed their time on the show and its lasting impact. If you're somehow unfamiliar with the extremely well-known series, "Friends" follows six close friends — Rachel (Jennifer Aniston), Monica (Courteney Cox), Phoebe (Lisa Kudrow), Joey (Matt LeBlanc), Chandler (Matthew Perry), and Ross (David Schwimmer) — as they navigate their romantic and work lives, living as twentysomethings in New York City.

The series is full of surprising moments and twists, beginning with Season 1, when Ross comes home from a trip with a new girlfriend, just as Rachel is ready to pursue a relationship with him. As the series progressed, we saw more shocks amongst the friends, from Chandler kissing Joey's girlfriend Kathy (Paget Brewster) to Ross and Rachel getting married while drunk in Las Vegas. Plus, who could forget the reveal that Rachel is the one who's pregnant, not Monica?

But, while all of these are undoubtedly crazy moments in television, there's one other plot twist that stands above the rest — delivered to us in the Season 4 finale.

In the Season 4 finale, most of the attention is on the show's resident will-they-won't-they couple, Ross and Rachel. And when Ross says his exes' name at the altar, it's undeniably a shock. However, it isn't that far-fetched that his connection to Rachel puts his marriage to Emily (Helen Baxendale) in danger. After all, they're set up from the beginning of the series as an endgame couple. However, the biggest plot twist comes when Monica and Chandler sleep together just before the wedding. The duo had never expressed any interest in each other romantically — outside of the occasional joke here and there — making the revelation that they just slept together a complete and utter shock to the viewer.

It turns out the writers were hoping for that kind of reaction. "Friends" executive producer and co-writer of the episode, Scott Silveri, told Vulture, "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 also revealed they filmed the episode three times through, in front of different audiences. He noted, "The first time ... 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."

As the series went on, Monica and Chandler's relationship acted as somewhat of a foil to Ross and Rachel's — instead of a very public will-they-won't-they, Monica and Chandler's union began as a secret and evolved into a very serious and committed relationship — one that ended with them married with two children. This new pairing gave fans a second relationship to root for, one of an entirely different dynamic.

Silveri told Vulture that the idea was brought up in previous seasons, but it wasn't until they were planning for Season 4 that they made their coupling a goal. He explained, "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. 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."

The plot twist of having Monica and Chandler sleep together in London had a lasting effect on the series, solidifying it as the biggest shock across 10 seasons. Silveri even noted that without this coupling, "Friends" probably would have ended three seasons sooner.