Brad Pitt – While he was still married to Jennifer Anniston, Brad Pitt played Ross' old high school friend who hated RachelNBC/Getty ImagesGeorge Clooney – Spoofing his E.R. fame, Clooney plays a dreamy doctor who takes care of Rachel's sprained ankleNBC/Getty ImagesAdam Goldberg – After Joey moved out, Adam Goldberg played Eddie, Chandler's creepy roommateNBC/Getty ImagesAisha Tyler – The Archer star played Charlie, a paleontologist who first dates Joey and then RossNBC/Getty ImagesAlec Baldwin – Alec Baldwin guest-starred as Pheobe's way-too-enthusiastic dateNBC/Getty ImagesAnna Faris – Anna Faris had a season-long role as Erica, whose twins Chandler and Monica adoptNBC/Getty ImagesBen Stiller – Ben Stiller appeared as Rachel's date who angrily yells at everyoneNBC/Getty ImagesBilly Crystal – Crystal plays one of two crazy strangers (with Robin Williams) whose conversation the friends overhear at Central PerkNBC/Getty ImagesRobin Williams – Williams plays that other crazy guy in Central PerkNBC/Getty ImagesBrooke Shields – Joey ends up regretting going on a date with his crazy stalker played by Brooke ShieldsNBC/Getty ImagesBruce Willis – Things get complicated when Rachel starts dating Paul Stevens (Bruce Willis), the father of a student Ross is datingNBC/Getty ImagesChristine Taylor – Rachel convinces Christine Taylor's Bonnie to shave her head so that Ross will break up with herNBC/Getty ImagesChristina Applegate – Along with Reese Witherspoon, Christina Applegate played one of Rachel's spoiled sistersNBC/Getty ImagesDermont Mulroney – Gavin, played by Dermot Mulroney, fills in for Rachel while she's on maternity leave and later becomes a love interestNBC/Getty ImagesCharlie Sheen – When Charlie Sheen's Navy man visits Phoebe for an erotic weekend, they both come down with chicken poxNBC/Getty ImagesCharlton Heston – Charlton Heston plays himself and gives Joey some acting adviceNBC/Getty ImagesDakota Fanning – Dakota Fanning offers Joey some advice on how to handle Chandler and Monica moving out of ManhattanNBC/Getty ImagesDanny DeVito – Danny DeVito plays a stripper at Phoebe's bachelorette partyNBC/Getty ImagesFreddie Prinze Jr. - Freddie Prinze Jr. is perfect as a sensitive male nanny who takes care of Ross and Rachel's daughterNBC/Getty ImagesHelen Hunt – In a confusing crossover, Hunt (a Mad About You star) mistakes Phoebe for her twin sister Ursula (a real character played by Lisa Kudrow in both Friends and Mad About You)NBC/Getty ImagesHugh Laurie – The stranger sitting next to Rachel on her flight to England (Hugh Laurie) mocks her plan to break up Ross' weddingNBC/Getty ImagesJay Leno – Leno plays himself interviewing Chandler's mom, an erotic novelist, on The Tonight ShowNBC/Getty ImagesJon Favreau – Jon Favreau spent almost a whole season as Monica's super-rich boyfriend who wants to become an Ultimate Fighting ChampionNBC/Getty ImagesJon Lovitz – Jon Lovitz guest-starred as a restauranteur in season one and a blind date for Rachel in season 9NBC/Getty ImagesJulia Roberts – Julia Roberts plays "Susie Underpants," a girl whose skirt Chandler pulled down on stage in elementary schoolNBC/Getty ImagesKristin Davis – The Sex and the City star is befriended by Rachel and Phoebe after she starts dating JoeyNBC/Getty ImagesReese Witherspoon – Reese Witherspoon guest-stars as Rachel's younger sister who goes on a date with RossNBC/Getty ImagesSean Penn – Phoebe must tell her twin sister Ursula's fiancée, played by Sean Penn, that Ursula has been lying to him about her pastNBC/Getty ImagesSusan Sarandon – In a plot line on Days of Our Lives, Joey gets Susan Sarandon's character's brainNBC/Getty ImagesTate Donovan – Real–life couple Jennifer Anniston and Tate Donovan played a couple on the show, tooNBC/Getty ImagesTom Selleck – Tom Selleck's mustachioed Dr. Richard Burke dates Monica on-and-off for several seasonsNBC/Getty Images
