Ever wonder how they came up with some of your favorite plot threads from Friends?

For example, we know how Monica ended up landing her date in the pilot, for instance, but how the did the writers decide where to go with, say, "The One with Ross's Wedding," given its significance in the storyline?

Thanks to Saul Austerlitz's Generation Friends: An Inside Look at the Show That Defined a Television Era, we can stop guessing and start marveling over how a simple mistake changed the course of the show forever. The book, comprised of a wide variety of interviews with the show's various creatives (writers, cast members, and more), has the inside scoop.

You may not believe that the way that episode ended up playing out was actually due to a mistake by Ross himself, David Schwimmer. When the entire cast heads to London for Ross's impending wedding to Emily (Helen Baxdale), something feels off. Ross isn't supposed to be with Emily! He's supposed to be with Rachel (Jennifer Aniston), right?

Well, according to Austerlitz, no one was initially sure how to end that episode. It wasn't definitive from the start that the wedding would actually go through successfully. But it wasn't until the team was rehearsing their lines one day that they would finally figure out how to approach this storyline's resolution. Schwimmer was supposed to say "Emily, the taxi's here," but ended up saying "Rachel, the taxi's here" instead.

"At that moment, "[producer] Greg Malins turned to [creator] David Crane and said, ‘That’s what happens.'," wrote Austerlitz. This simple mistake lead to Schwimmer changing the course of the show, with Ross ending up vowing to take Rachel at his wedding instead of Emily. You probably know how things played out from there, but it's crazy how one simple slip like this ended up being such a pivotal move for the series and Ross and Rachel shippers.

So, if you're a hardcore Ross and Rachel fan, you can thank David Schwimmer for getting things kicked off on the right foot there. Who knew?