Friends almost had to write Jennifer Aniston out of the show

L to R: Aniston, David Schwimmer, Courteney Cox, Matt Leblanc, Lisa Kudrow and Matthew Perry. Photo / Getty Images

A bombshell new book claims Jennifer Aniston was almost removed from the '90s sitcom Friends.

The book, Generation Friends, reveals the show's writers nearly had to recast Aniston's on-screen character Rachel Green because of conflict with another show's project, according to The Sun.

It turns out Jennifer Aniston, an unknown actress at the time, had filmed several episodes of another new comedy called Muddling Through for a rival network before her 1994 Friends audition.

Friends bosses were desperate for the actress to play Central Perk waitress Rachel, but the book alleges they were concerned they would lose Aniston halfway through filming the first season if the other show Muddling Through was picked up for a full series.

The US network channel NBC that aired Friends for 10 seasons decided to 'kill' the rival show by scheduling a series of blockbuster movies against it during the summer.

As a result, Muddling Through was axed, Aniston got the Friends gig, and the rest is history.

Actress Jennifer Aniston stars as Rachel Green in Friends. Photo / Getty Images

Saul Austerlitz' fascinating behind-the-scenes tell-all book is released next month to coincide with the show's 25th anniversary.

The book also reveals network bosses wanted to add a "seventh friend" into the mix alongside Rachel, Monica (Courteney Cox), Phoebe (Lisa Kudrow), Ross (David Schwimmer), Chandler (Matthew Perry) and Joey (Matt Leblanc).

"The one major suggestion the network had was the addition of an older secondary character," writes Austerlitz.

The writers then came up with a character known as "Pat The Cop" who would have rubbed shoulders with the gang.

"The writers made a good-faith attempt, even casting the role, but hated the resulting script so much that they pleaded with NBC to drop the idea," reveals the book. "NBC gave its permission and Pat the Cop was no longer."

Even Courteney Cox almost lost out on the role of Monica, the book reveals.

Janeane Garofalo in The Matchmaker. Photo / News Corp Australia

The bosses initially cast actress Janeane Garofalo in the role before Cox claimed her position.

Monica was also envisioned to be a "tough, cynical, sarcastic" character before reworking their vision.