As part of the nostalgic flurry that is Friends' 25th anniversary, pop culture historian, writer, and professor Saul Austerlitz's Generation Friendshit bookstores on Sept. 17th.

Austerlitz's examination of the landmark show explains how it all came together through extensive interviews with Friends creators David Crane and Marta Kauffman and producer Kevin Bright. In fact, Generation Friends is so remarkably thorough that most of the names listed in that signature white Friends font during the show's credits contributed to the book.

In addition to reckoning with how the show's more outdated and downright offensive plot developments and jokes have (or haven't) stood the test of time, Generation Friends includes countless behind-the-scenes tidbits that cast the show in a whole new light.

Not only does Austerlitz add nuance to Ross, Rachel, Phoebe, Joey, Monica, and Chandler's characters, he gives us insight into the lives of David Schwimmer, Jennifer Aniston, Lisa Kudrow, Matt LeBlanc, Courtney Cox, and Matthew Perry as well.

After devouring the book ourselves, we've gathered eight of the juiciest backstage secrets.

1. Joey and Monica were supposed to be the central romance of the show, and other casting surprises

You read that right.

Monica and Joey, two characters who never had the faintest bit of onscreen chemistry, were slated by Crane and Kauffman as the only two of the six leads who would eventually end up together. However, after revising the character of Joey to make him a more believable fit within the group, Joey (and LeBlanc's role-winning take on him) were too likable to fit the bad boy stereotype that Monica was supposed to fall for. So, their romance — and the rough and tough version of Joey — ended up on the cutting room floor.

Who's going to tell Joey that he technically had a chance with Monica way before Chandler did?Credit: giphy

More surprisingly, it was only after seeing Aniston and Schwimmer read together that Kauffman and Crane even considered a romance between Ross and Rachel. Although the show portrays the couple as written in the stars throughout all ten seasons, audiences really have Aniston and Schwimmer's natural chemistry (and Kauffman, Crane, and Bright's instincts) to thank.

SEE ALSO:'Friends' is turning 25. Here are the 15 best episodes.

Austerlitz reveals the role of Ross was written with Schwimmer in mind, specifically. After convincing Schwimmer to take his chances on a television role, despite his aversion to the medium, Ross was the first role Kauffman and Crane cast. But Kudrow had actually been cast as the original Roz Doyle in Frasier — she was quickly fired after not being able to match Kelsey Grammer's intensity.

In other words, in being cast first as Roz and later Phoebe Buffay, Kudrow landed two separate, iconic main roles on two of the most classic sitcoms ever, even if only one made her a star. (Both also ran for ten years and wrapped up their runs in May 2004.)

Peri Gilpin, who replaced Kudrow as Roz Doyle, giving it to Grammer's Frasier — just as producers intended.Credit: giphy

2. Nixed storylines

Generation Friends takes readers into the writers' room where all the story ideas that populated Friends episodes originated. Much like the what-if episode "The One That Could Have Been," not only do readers learn about how their favorite Friends moments were created, we also learn about those oddball ideas that didn't make it onscreen.

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The show's writers delighted in giving fans plot twists and cliffhangers that no one would expect — but there was one Crane shut down immediately. Friendswriters had envisioned a change of pace for the show in which the New York crew follows Chandler who has been relocated to the Midwest for work — yes, they were raving about shifting the entire setting to Minnesota. The satellite storyline was only supposed to last half a season, but Friends fans are surely glad it never materialized at all.

Much to the cast's chagrin, Rachel and Joey got past just "How you doin?"Credit: Giphy

Austerlitz also describes how Perry, Cox, LeBlanc, Kudrow, Aniston, and Schwimmer would nix storylines that they didn't want to perform, or didn't find believable. Perry, for example, refused to portray Chandler's affinity for the tuna melts served at a local gay bar.

What's more satisfying, however, is the fact that the cast themselves disliked the idea of a romance between Rachel and Joey. Crane convinced the cast and crew to go forward with it anyway for the sake of an emotional storyline for Joey's character. Clearly the actors on Friends predicted how much the pairing of Rachel and Joey would be despised by most of the show's millions of viewers.

SEE ALSO:The 'Friends' theme song takes a dark turn when played in a minor key

3. Choice plot lines were inspired by Jane Austen

As Austerlitz tells it, writer Jeff Greenstein had read all of Jane Austen's novels by the time he entered the Friends writers room because his wife had written her senior thesis on the author. So when it came time to fashion Ross and Rachel's romantic climax at the end of the show's first season, Greenstein was inspired to come up with the scenario of Ross giving Rachel the brooch for her birthday, only to leave on a trip China just in time for Rachel to realize his feelings for her, and that they're reciprocated on her end.

Whereas Greenstein described the aforementioned scenario as textbook Austen, the pros and cons list Ross writes to compare Rachel and Julie in season two is a more direct nod to Austen's Pride and Prejudice. So if you recognized the similarities between Ross's major flub and Mr. Darcy's first proposal, Austerlitz confirms your suspicions.

4. The hairdresser who created "The Rachel" was high when he did so

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"The Rachel" consisted of partial bangs and layers and was created by Chris McMillan. Austerlitz revealed that mid-90s' most popular haircut was the brainchild of an under-the-influence McMillan.

Austerlitz also notes that "the Rachel" fever was so widespread that hairdressers across the nation began refusing to do the cut and style on clients.

5. The show's creators never had a set plan for the show

Although one of the show's greatest critiques is that realistically, thosesix people couldn't lead their onscreen lives in the real world, Kauffman and Crane created such a rich ten-season storyline through attention to detail and an immense commitment to the Friends universe — not through a grand plan. According to Austerlitz, the showrunners were "only ever a few episodes ahead of the curve." Kauffman and Crane might have had an idea of how the season they were currently working on might end, but nothing was set in stone.

Case in point: The third season's finale, in which the gang and Ross's girlfriend Bonnie (Christine Taylor) are staying at a beach house. Ross and Rachel kiss, and the season ended on a cliffhanger: a shot of Ross being left to choose between Rachel and Bonnie, represented by the doors to both rooms in which each women was staying at the beach house. The Friends writers' room did not know which woman Ross would pick, choosing to end the season on a single word that worked either way: "Hi."

Ross's mystery doors.Credit: warner brothers/screenshot

6. All you need to know about "Could I bewearing any more clothes?"

Ranked number 15 on Mashable's list of the best Friends episodes, "The One Where No One Is Ready" is mostly known for Joey's triumphant moment in which he struts into Monica and Rachel's apartment sporting all of Chandler's clothes at once in retaliation for Chandler hiding all his underwear, forcing him to go commando in a rented tux. Mocking his roommate's signature sarcastic style, Joey inquires "Could I bewearing any more clothes?" and follows through on his threat to do lunges.

Well, probably, butCredit: giphy/nbc

Through interviews with the show's longtime costume designer, Debra McGuire, Austerlitz learned that the monstrosity LeBlanc is wearing was actually a two-piece suit that the actor stepped into. Each of the fabrics were stitched together to allow for easy maneuvering in and out of the costume.

Speaking of Joey's dire lack of underwear, the show played a vital part in popularizing the term "going commando." Generation Friends reveals that Crane and Kauffman had never heard the term before the episode's storyline was crafted. At the persistence of the rest of the writing staff, the phrase made it on the show — and to prove its influence, Austerlitz points to the Oxford English Dictionary crediting Friends for one of the earliest uses of the term.

7. Owen Wilson was going to guest star

Friends is known for his impressive range of guest stars, some of whom went on to epic stardom (Reese Witherspoon, Paul Rudd, Hugh Laurie) and others who aren't seen on-screen as much nowadays (Elle MacPherson, Charlie Sheen). Among one of the former sorts of celebrities who later achieved great success is Owen Wilson, whose guest starring spot was pulled from one season's twentieth episode before he was contacted for the part. The Friends writers became wary of an infamous interview which portrayed Wilson as difficult to work with; in particular, he admitted that he "gave writers a hard time." That self-aware quip was enough to squash any dreams Wilson might've harbored of being on the show.

8. The cast and crew cried when saying goodbye to the iconic Central Perk couch during the finale... and then drank tequila as they watched the set being torn apart

According to Austerlitz, one of the first scenes filmed for the show's two-part finale was Friends' last hurrah at Central Perk. As expected, the cast and crew savored the gang's final bantering moments on the iconic couch: after the scene wrapped, the actors, creators, and most of the other people working on the show at its close gathered on the set to hug, cry, and share in what was only the first of many goodbyes.

Because another show was to shoot on the Warner Brothers lot that Friends had occupied for ten years immediately after Friends wrapped, the set was dismantled right after the gang exited Central Perk for the last time. So, the cast and crew drank tequila in celebration and sorrow of the show, and set pieces, ending.

And the entire Friends team signed the back of the coffeehouse set to memorialize the show, and the moment.

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