Asking someone whether they’ve seen Friends is often considered an insult in the English language.

After the show kept us emotionally invested in everything from the colour of Gunther’s hair to the pitch of Janice’s voice, we admit that we can get a little precious about how much time we’ve spent obsessing over the finer details of the greatest sit-com of our time.

Which is why it felt like a nasty mind-bending exercise when Courteney Cox revealed in the Friends reunion last year that she was originally slated to play Rachel.

Yes, you read it correctly. Cox originally auditioned for Aniston’s part, and it was only at the last minute that she changed her mind and decided to play the germ-hating Monica Geller.

Read more: Why Friends was and is still a TV phenomenon 

Which is almost as difficult to comprehend as that moment we discovered that Monica and Joey were meant to be a couple in the landmark TV series.

Speaking about the change in casting for the first time, Cox said that she decided to play Monica because she “related more” to the character.

"For some reason, I thought I related more to Monica, which is maybe because I do," Cox said on the US interview programme Off Camera With Sam Jones.

"I'm very similar to her. I'm not as clean as Monica, but I'm neat. And I'm not as competitive, even though some people, my partner Johnny McDaid, would say I am."

Cox added that the success of the show was down to one thing – the chemistry between the team.

Read more: What the minor Friends stars are doing now

 “I knew during the pilot... I could tell it just worked,” she recalled to Jones. “People responded to it. It felt right.

"That was lightening in a bottle, to have those writers, those creators of the show and the team they put together it just worked," she said. "It was just a group of great people that were put together that were there for the right reason."

Pictures: Rex Features