The hugely popular US sitcom, which followed a group of New Yorkers in their twenties and thirties, concluded in 2004 after 10 seasons.
Seeing all six principal cast members get back together to discuss their time on the show is genuinely rare. In recent years, journalists have generally been told not to ask any Friends questions when interviewing the show's former stars.
Table reads, trivia games, fashion shows, archive clips and celebrity interviews are woven into the 1hr 39min reunion, which was made available to the press on Wednesday.
Reactions to the special have been broadly positive so far, although many critics noted some elements of the show work better than others. Rolling Stone described it as "an overproduced affair with too many guest stars and detours", but added: "When it lets the iconic gang of six just talk amongst themselves, it hits the nostalgic sweet spot."
Friends: The Reunion is available in the UK on the streaming service Now, and will also air on Sky One at 20:00 BST on Thursday. Here are 10 of the best moments:
1. 'Everything seems smaller'
The special opens with David Schwimmer arriving at the Warner Bros studios to visit the reconstructed Friends sets, including the two main apartments and the coffee house, Central Perk. He is followed by the other cast members one by one, most of whom become emotional as they reunite.
"It all seems small to me, the whole stage," notes Matt LeBlanc. "That's impossible though, because we haven't grown," replies Aniston. An awkward moment passes before LeBlanc jokes, with perfect timing: "Speak for yourself." (He is admittedly quite a bit bigger now.)
It isn't long before they're sharing memories. LeBlanc reminds Courteney Cox about how she would scribble her lines on the kitchen table, beside the fruit bowl.
"You had this big speech," he says, "you were struggling with it all week long, and you wrote it on the table. And when you weren't looking I erased it and you got so mad at me!" Cox laughs about it now, recalling: "I had so much dialogue hidden in these apples."
2. The cast have no recollection of some episodes
Matthew Perry has previously said he doesn't remember three whole years of his time on Friends - but it turns out he isn't the only one.
When Aniston brings up season five's The One With The Ball, in which the group all get involved in a game of catch for hours on end, Schwimmer admits: "I don't remember that," while looking genuinely puzzled.
"There are seasons I've never seen," Kudrow admits later. "Michel [Stern, her husband] and I started watching some of season four, which I thought I had watched. He enjoys them more than I do, because I'm mortified with myself."
Perry also hasn't revisited the show, while Schwimmer says: "I hadn't seen it really in 17 years, until my daughter just started watching it this past year, and that kind of sucked me into it."
But the others haven't shied away from it as much - LeBlanc and Cox both reckon they've seen every episode.
"I was so proud to be on the show, some of the stuff was so great," says LeBlanc, before recalling a favourite scene involving Ross and his new trousers from The One With All The Resolutions. "That thing with the leather pants, that still cracks me up," he says.
"That was on the other day, I just happened to be in the kitchen with Marina [his daughter], we were eating dinner, and I said to her 'watch this, this is funny, watch David'."
3. There are some glorious new outtakes
Having watched countless Friends blooper-reels on YouTube over the years, we didn't think there were any outtakes we hadn't seen.
But it turns out there are a couple in the vault which are unleashed for the first time in the reunion.
There's one truly filthy unscripted joke we can't repeat here, during a scene where Monica and Chandler are in bed.
And another where Perry does a hilarious dance when he can't remember his line, only for LeBlanc and Schwimmer to repeat the same dance behind him when he tries to do a re-take.
4. Perry's need for laughs 'wasn't healthy'
Perry probably gets the least screen time of the main six during the reunion, and when the trailer was released some fans expressed concern about his appearance and speech (his previous struggles with addiction have been well-documented).
But he does speak movingly about how deeply affected he was by some parts of the job, and in particular seeking validation from the show's live audiences.
"I felt like I was going to die if they didn't laugh," he says. "And it's not healthy, for sure. But I would sometimes say a line and they wouldn't laugh and I would sweat, and go into convulsions. If I didn't get the laugh I was supposed to get, I would freak out. I felt like that every single night."
He later recalls how he interrupted the filming of one scene after LeBlanc accidentally tripped over the carpet, much to the audience's delight. "I was like, somebody's getting a laugh, I can't handle it, I need to get a laugh too," Perry said.
The actor's desire for audience approval has evidently impacted all of his work. When his play The End of Longing debuted in London in 2016, it went through several re-writes during the course of its run, with multiple new jokes added as the weeks went by. Audience members (including us) who saw the show multiple times were surprised to find brand new chunks of dialogue in later performances.
5. Warning: One scene is not for the squeamish
Series three's The One Where No-One's Ready is a fan favourite, and most will recall the storyline where Chandler and Joey are fighting over an armchair. At one point in the episode, they both dive for it at the same time, with Joey ultimately making it there first after hurling himself over the furniture.
"We shot it three times and it went perfectly," recalls co-creator Marta Kauffman. "Lord knows why we had to shoot it a fourth time."
LeBlanc picks up the story: "I went to jump over the coffee table, somehow tripped, my legs went up in the air, and my shoulder came out of its socket."
Eeesh. LeBlanc has told this story before on Jimmy Kimmel, but in the reunion we actually get to see the original footage - in which his arm looks separated from his body. "In come all the paramedics, they've got to take him to the hospital, and that was the end of filming," says co-creator David Crane.
The actor's dislocated shoulder was written into subsequent episodes, but the writers had Joey sustain the injury off-screen while jumping on his bed to explain why his arm was in a sling.
6. The trivia quiz is back
Schwimmer recreates his quiz from series four, where the boys and girls compete with one another to see who knows each other better.
In one new round of questions, Schwimmer asks the female cast members to identify a character from an audio clip taken from an early episode. "That's my monkey," the mystery voice says.
"Mr Hinkle?" ventures Kudrow. "No, what's his name?"
"It's the guy who lives downstairs," says Aniston, trying to place him. "Mr Wriggles?"
You've probably guessed that the correct answer is the ever-grumpy Mr Heckles. Fortunately, they do better on some of the other rounds.
7. There's no shortage of A-listers
Some celebrities get heavily involved in the games and activities. We won't spoil those here but there's an extremely special guest duetting with Kudrow on Smelly Cat. Other stars simply appear briefly to share the influence Friends had on their lives.
"My mum bought me the DVDs of the whole series when I was in elementary school," explains RM of Korean boyband BTS. "Friends really had a big hand in teaching me English." (We've heard this story before but it's still a nice anecdote).
Meanwhile, Nobel Peace Prize-winner Malala Yousafzai reveals she has a soft spot for The One With The Routine, comic Mindy Kaling likes The One with All The Kissing, and actor Kit Harington particularly admires the "pivot" sequence in season five - where Ross, Chandler and Rachel are trying to get a couch up the stairs.
"I'd have to say I'm most like Monica, because I'm a clean freak," reflects footballer David Beckham. "I travel a lot, I'm always in hotels, I've always got down time, when I'm missing the kids, missing the family, I put on Friends, because it makes me smile."
8. Fake Joey was almost Real Joey
Creators Kauffman and Crane and director Kevin Bright share many behind-the-scenes stories. Friends scholars will have heard many of them before, like how Cox originally auditioned for Rachel before being cast as Monica.
But there are some new nuggets here too. Bright recalls the tough audition process for casting Joey. He says it "went down to the wire" with LeBlanc and another actor.
"But the funny thing about it is the other actor ended up in the show, in The One With Unagi. Playing Fake Joey, ironically."
That means the other actor in the running was Louis Mandylor, who appears in the season six episode as part of a plot line where Joey is trying to earn money by pretending he has an identical twin.
9. Friends of Friends show up throughout
ames Corden asks the group who has the loudest and most distinctive laugh, at which point everyone looks towards Kudrow.
But then: "Oh. My God! I can't believe you didn't say me!" yells Maggie Wheeler (who played Janice) from the side of the stage, surprising the cast and joining them for a chat on the famous sofa.
James Michael Tyler, who played Gunther, is the only guest who joins via Zoom. "It was the most memorable 10 years of my life," he says, "I could not have imagined a better experience."
Was there anyone the cast didn't like while working on the show?
"The monkey," LeBlanc and Schwimmer both reply instantly, referring to Ross's series one companion, Marcel.
"I'm an animal lover," says Schwimmer, "but what inevitably began to happen was that [scenes] would get messed up because the monkey didn't do its job right. So we'd have to re-set, we'd have to go again... this kept happening, over and over."
10. Friends: The Movie?
It isn't easy for a series to maintain razor-sharp writing, relatable characters, well-observed storylines, great on-screen chemistry and high viewing figures for 10 years. But Friends did it - and without ever jumping the shark (although it came pretty close in the final season, with a weak episode literally titled The One With The Sharks).
Fans of the US sitcom often say, only half-jokingly, that every situation in life can be related to a Friends storyline. And while some sections of this reunion do feel a little padded out, ultimately this is a classy and enjoyable special which won't disappoint devotees.
For years, many fans have been desperate for a scripted reunion - with the stars reprising their roles in a new series or film. But you can guess how the cast react to being asked by Corden whether they've considered it.
"No. I'm sorry, I haven't," says Kudrow. "I once heard Marta and David say, and I completely agree, that they ended the show very nicely, everyone's lives are very nice, and they would have to unravel all those good things in order for there to be stories. And I don't want anyone's happy ending unravelled. Also, at my age, to be 'floopy'? Stop. You have to grow up."