co-stars David Schwimmer and Jennifer Aniston revealed they almost had a real-life romance to rival that of their characters Ross and Rachel.
The revelation came in the beloved comedy's long-awaited reunion, which brought the cast back together on screen for the first time since the show ended its celebrated 10-year run in 2004.
Schwimmer and Aniston were joined by co-stars Courteney Cox, Lisa Kudrow, Matt LeBlanc and Matthew Perry for a nostalgia-fuelled two-hour special reliving some of' most famous moments.
Filmed on the show's set at the Warner Bros studios in Burbank, California, it included a cavalcade of celebrity cameos, from famous fans to A-list supporting characters.
Perhaps the special's most startling moment was the news that Schwimmer, 54, and Aniston, 52, came close to a relationship off-screen.
Their characters, paleontologist Ross Geller and fashionista Rachel Green, were famously involved in a will-they-won't-they romance storyline over the 10 seasons.
Asked by reunion host James Corden if any of the stars ever grew close, Schwimmer said: "The first season I had a major crush on Jen. And I think we both, at some point, were crushing hard on each other but it was like two ships passing because one of us was always in a relationship and we never crossed that boundary. We respected that."
LeBlanc, who played ladies' man Joey Tribbiani, coughed: "Bullshit."
"It's true!" Schwimmer protested, while the cast were seated in front of the fountain from the show's opening credits.
Aniston agreed and said their first kiss did indeed come on TV, when they embraced at Central Perk, the coffee shop where the gang spent much of their time.
Schwimmer later admitted he was surprised that those on set were not aware of his feelings for Aniston due to their overt flirting, only for his co-stars to insist: "We knew."
Elsewhere, it was revealed that LeBlanc dislocated his shoulder while filming a stunt requiring him to jump into a chair to annoy Perry's Chandler Bing.
While shooting season three's 'The One Where No One's Ready', LeBlanc jumped on to the chair three times — but on the fourth attempt he slipped and his shoulder came out of its socket.
Footage of the incident was shown during the special and revealed the actor's arm noticeably lower than it should have been.
Filming was stopped for the day so he could receive medical attention.
While the cast's chemistry was obvious to viewers, it emerged that one character was not so liked by the others.
Schwimmer actually had a strong dislike of Marcel, Ross's pet white-headed capuchin monkey.
He said not only would the animal mess up their well-orchestrated takes, but his handler would feed him live bugs during filming, which he would then eat and proceed to wipe his dirty hands on Schwimmer.
Kudrow, 57, played eccentric masseuse Phoebe Buffay. She was joined by Lady Gaga for a rendition of Phoebe's trademark song 'Smelly Cat'.
Seated on the sofa in Central Perk, pop star and actress Gaga delivered a typically rousing performance, which included a subtle nod to. They were later joined by gospel singers.
Kudrow, having slipped into character, muttered: "Still think it's better when it's just me."
Gaga agreed and thanked her for being "the different one" on the show.
Members of' weird and wonderful supporting cast also made cameos.
Larry Hankin returned as noisy neighbour Mr Heckles, Thomas Lennon appeared as Joey's hand twin, and James Michael Tyler, who played Gunther, the coffee shop manager in love with Rachel, Zoomed in to the special.
A-lister Tom Selleck played Richard, the older boyfriend of Cox's Monica Geller, and featured during the reunion, as did Janice actress Maggie Wheeler.
Elliott Gould and Christina Pickles, who starred as the Gellers' parents, spoke to the cast from the audience.
Producers squeezed in more celebrity guests with a fashion show ofoutfits, with Justin Bieber, Cindy Crawford and Cara Delevingne all strutting their stuff on the catwalk.
During the reunion's emotional climax, Corden asked Kudrow her thoughts on furtherepisodes or the possibility of a film.
She dismissed the idea, referring to previous statements by co-creators David Crane and Marta Kauffman about the show having a perfect ending.
Asked if she had contemplated more, Kudrow said: "No, I'm sorry I haven't.
"Because that's all up to Marta and David, and I once heard them 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."