01of 14Julia RobertsNBCIt’s hard to imagine a world in which anyone would turn down Roberts, but it happened inFriends. She played Chandler’s elementary school classmate Susie Moss, whom he humiliated in the fourth grade after he lifted her skirt up during a school play, and “the entire auditorium saw my underpants,” as she recalled. She finally gets him back decades later when she seduces him in a bathroom stall and then steals his clothes in season 2’s “The One After the Super Bowl.”
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Julia Roberts
NBC

It’s hard to imagine a world in which anyone would turn down Roberts, but it happened inFriends. She played Chandler’s elementary school classmate Susie Moss, whom he humiliated in the fourth grade after he lifted her skirt up during a school play, and “the entire auditorium saw my underpants,” as she recalled. She finally gets him back decades later when she seduces him in a bathroom stall and then steals his clothes in season 2’s “The One After the Super Bowl.”
02of 14Charlie SheenGary Null/NBCTheTwo and a Half Menstar was in the season 2 episode “The One with the Chicken Pox,” in which he played an ex-boyfriend of Phoebe’s — a sailor who spends years at a time living in a submarine. When he’s above ground for two weeks to spend some time with Phoebe, however, the two come down with the chicken pox — but manage to make his stay romantic regardless.
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Charlie Sheen
Gary Null/NBC

TheTwo and a Half Menstar was in the season 2 episode “The One with the Chicken Pox,” in which he played an ex-boyfriend of Phoebe’s — a sailor who spends years at a time living in a submarine. When he’s above ground for two weeks to spend some time with Phoebe, however, the two come down with the chicken pox — but manage to make his stay romantic regardless.
03of 14Hugh LaurieNBCYou know that talkative, foot-tapping person youneverwant to get stuck next to on a plane? Rachel was that person for Laurie, who played a hilarious, very annoyed Brit on a flight from New York City to London (where Rachel was headed to try and stop Ross and Emily’s wedding) in the season 4 episode “The One with Ross’s Wedding.”
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Hugh Laurie

You know that talkative, foot-tapping person youneverwant to get stuck next to on a plane? Rachel was that person for Laurie, who played a hilarious, very annoyed Brit on a flight from New York City to London (where Rachel was headed to try and stop Ross and Emily’s wedding) in the season 4 episode “The One with Ross’s Wedding.”
04of 14Susan SarandonNBCJoey gets a second chance at soap stardom in the season 7 episode, “The One with Joey’s New Brain,” after he learns that his character Dr. Drake Ramoray, who had been in a coma for five years, is getting a new brain. Said new brain comes from Sarandon’s Jessica Lockhart, a veteran soap star and egomaniac.
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Susan Sarandon

Joey gets a second chance at soap stardom in the season 7 episode, “The One with Joey’s New Brain,” after he learns that his character Dr. Drake Ramoray, who had been in a coma for five years, is getting a new brain. Said new brain comes from Sarandon’s Jessica Lockhart, a veteran soap star and egomaniac.
05of 14Kathleen TurnerNeal Peters Collection/NBCWe first met the former Charles Bing — now Helena Handbasket, Chandler’s transgender father — in season 7’s “The One with Chandler’s Dad,” when she’s on-stage in her drag show,Viva Las Gaygas.
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Kathleen Turner
Neal Peters Collection/NBC

We first met the former Charles Bing — now Helena Handbasket, Chandler’s transgender father — in season 7’s “The One with Chandler’s Dad,” when she’s on-stage in her drag show,Viva Las Gaygas.
06of 14George Clooney & Noah WyleFotos International/GettyTheERstars made an appearance on their fellow NBC show as a pair of doctors (of course) who try to date Rachel and Monica — after they’ve committed insurance fraud in the season 1 episode, “The One with Two Parts.”
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George Clooney & Noah Wyle
Fotos International/Getty

TheERstars made an appearance on their fellow NBC show as a pair of doctors (of course) who try to date Rachel and Monica — after they’ve committed insurance fraud in the season 1 episode, “The One with Two Parts.”
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Winona Ryder

08of 14Bruce WillisChris Haston/NBCWillis played the ultimate scary, overprotective pop in season 6’s “The One Where Ross Meets Elizabeth’s Dad.” Not only did he hate Ross, he also dated his ex — Rachel!
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Bruce Willis
Chris Haston/NBC

Willis played the ultimate scary, overprotective pop in season 6’s “The One Where Ross Meets Elizabeth’s Dad.” Not only did he hate Ross, he also dated his ex — Rachel!
09of 14Jason AlexanderWarner Bros. TelevisionAlexander hopped from one legendary comedy to another when he appeared in the season 7 episode “The One Where Rosita Dies” as a miserable office manager whom Phoebe encounters while trying to sell him toner as a telemarketer.
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Jason Alexander
Warner Bros. Television

Alexander hopped from one legendary comedy to another when he appeared in the season 7 episode “The One Where Rosita Dies” as a miserable office manager whom Phoebe encounters while trying to sell him toner as a telemarketer.
10of 14Brad PittDanny Feld/NBCJennifer Aniston’s then-husband guest-starred on the season 8 Thanksgiving episode “The One with the Rumor” as a former high school classmate of Ross, Monica and Rachel’s — who had a pure, unadulterated hatred of Rachel.
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Brad Pitt
Danny Feld/NBC

Jennifer Aniston’s then-husband guest-starred on the season 8 Thanksgiving episode “The One with the Rumor” as a former high school classmate of Ross, Monica and Rachel’s — who had a pure, unadulterated hatred of Rachel.
11of 14Reese WitherspoonNBCRachel’s sister Jill attempted to well, pull a Rachel, leaving home and vowing to stop using their father’s credits cards in the season 6 episode “The One with Rachel’s Sister.” The whole thing blows up, however, when she tries to date Ross, eventually deciding to go back to a bankrolled lifestyle.
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Reese Witherspoon

Rachel’s sister Jill attempted to well, pull a Rachel, leaving home and vowing to stop using their father’s credits cards in the season 6 episode “The One with Rachel’s Sister.” The whole thing blows up, however, when she tries to date Ross, eventually deciding to go back to a bankrolled lifestyle.
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Danny DeVito

13of 14Sean PennNBCIn the season 8 episode “The One with the Halloween Party,” we met Eric, a sweet school teacher who is engaged to Phoebe’s twin Ursula, thinking that she’s a similarly sweet teacher. After Phoebe breaks the news, they date for a bit — until he realizes he can’t stand the sight of Ursula, and therefore, Phoebe too.
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Sean Penn

In the season 8 episode “The One with the Halloween Party,” we met Eric, a sweet school teacher who is engaged to Phoebe’s twin Ursula, thinking that she’s a similarly sweet teacher. After Phoebe breaks the news, they date for a bit — until he realizes he can’t stand the sight of Ursula, and therefore, Phoebe too.
14of 14Alec BaldwinNBCIn “The One with the Halloween Party” in season 8, Baldwin played a short-lived boyfriend of Phoebe’s who is excited aboutliterally everything.
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Alec Baldwin

In “The One with the Halloween Party” in season 8, Baldwin played a short-lived boyfriend of Phoebe’s who is excited aboutliterally everything.
source: people.com