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When Courteney Cox was on The Tonight Show with Jay Leno (1992), she told Jay this story about filming Friends (1994). On set one day, Cox kept reciting a line by Anthony Michael Hall, saying, "Chicks cannot hold their smoke; that's what it is." Matthew Perry thought it was from Weird Science (1985), but Cox was adamant it was from The Breakfast Club (1985). After asking around among sound men, production staff, et cetera, they couldn't come up with a definitive answer, and they began betting on it, starting at twenty dollars and then raising the stakes. Perry joked that if he won, Cox would have to sleep with him, and if she won, he would have to sleep with her. When they heard that Judd Nelson (Hall's castmate in The Breakfast Club) was filming Suddenly Susan (1996) on a nearby stage, they went over and asked him and found out the quote was indeed from The Breakfast Club. Leno asked Cox what the bet was, to which Cox sneezed and then rang a bell. Perry walked out from backstage with a tissue in his hand. Cox told Leno that Perry would be her man slave for five more months.
Joey was originally written as a jerk. When Matt LeBlanc questioned why the others would be friends with him, the character was changed.
When Matt LeBlanc auditioned for the role of Joey, he had eleven dollars to his name. When the cast got their first paychecks, the first thing that LeBlanc bought was a hot dinner. Courteney Cox bought a car.
When Courteney Cox dressed as fat Monica for the first time, Matthew Perry walked right past her without recognizing her.
Courteney Cox was originally supposed to play Rachel. In Friends: The Reunion (2021), she explained that she asked to play Monica instead, since she related to her more.
Lisa Kudrow and her best friend wrote "Smelly Cat" one night when they were drunk, and it eventually got written into the show.