20 Best Celebrity Guest Stars On Friends

Season 9, Episode 22: The One with the Donor

John Stamos guest stars as Zack, an unsuspecting sperm donor for Chandler and Monica. Zack is unknowlingly invited to dinner as a test to see if he will be a fitting donor. The couple scares him away, though, because of all the random health-related questions. This marks the turning point for Chandler and Monica, and they ultimately decide to adopt a baby instead.

Season 3, Episode 22: The One with the Screamer

Rachel brings a date (Ben Stiller) to the opening of Joey's play, but he turns out to be extremely short-tempered and yells at everyone for the slightest inconveniences.

Season 3, Episode 24: The One with the Ultimate Fighting Champion

Robin Williams and Billy Crystal burst onto screen by interrupting a conversation with the six friends, insisting that they make room for the two guest stars because there are no other open seats in Central Perk. Robin Williams' character mentions that he suspects his wife is cheating on him. The friends soon learn that Billy Crystal's character is the one who is sleeping with her.

Season 8, Episode 6: The One with the Halloween Party

Season 8, Episode 7: The One with the Stain

Eric (Sean Penn) is originally engaged to Ursula, Phoebe's identical twin sister. Phoebe learns that Ursula lies in order to keep their relationship going, so she reveals this information to Eric. Eric and Phoebe develop feelings for one another, but Eric sleeps with Ursula, thinking that she is really Phoebe.

Season 2, Episode 12: The One After the Superbowl: Part 1

Brooke Shields (Erika) plays a crazed fan of Dr. Drake Ramore, Joey's soap opera character. Erika sends Joey fan-mail, and the two eventually meet for dinner. However, Erika believes that Joey is actually Dr. Drake Ramore, and after a few glasses of wine, she also starts to believe that the two are engaged.

Season 10, Episode 14: The One with Princess Consuela

Chandler and Monica take Joey to see their new house, but Joey fears that he will lose them as friends when they move. Mackenzie (Dakota Fanning) ultimately helps Joey realize that Chandler and Monica will be happier in their new house.

Season 1, Episode 17: The One with Two Parts (2)

In efforts to boost ratings, ER doctors George Clooney and Noah Wyle joined the cast of Friends for an episode, fittingly playing another set of doctors. When Rachel Green sprains her ankle, she changes her name at the hospital in order to use Monica's health insurance. The studly doctors ask Monica (Rachel) and Rachel (Monica) on a date, and, in true sitcom-y fashion, hijinks ensue.

Season 9, Episode 8: The One with Rachel's Other Sister

Season 10, Episode 5: The One Where Rachel's Sister Babysits

It's a shame there wasn't an episode where all three Green sisters (Jennifer Aniston, Reese Witherspoon, and Christina Applegate) get to interact with each other. Still, Applegate held her own. Applegate's character gets Emma's ears pierced when she babysits for Rachel.

Season 8, Episode 17: The One with the Tea Leaves

Season 8, Episode 18: The One in Massapequa

Alec Baldwin plays the extremely enthusiastic Parker, a man who Phoebe meets at the Gellars' 35th wedding anniversary party. Parker compliments everyone and everything, but this becomes annoying to the partygoers.

Season 2, Episode Episode 13: The One After the Superbowl: Part 2

Julia Roberts, aka Susie "Underpants" Moss, was a childhood friend of Chandler's. Year's ago, Chandler pulled down Susie's pants in front of the whole school, thus revealing her underwear. Viewing their reunion as the perfect opportunity for revenge, Susie goes on a date with Chandler and tricks him into wearing her underwear, leaving him stranded without any other clothes.

Season 10, Episode 3: The One with Ross' Tan

She had sex with Evel Knievel and was a perfect arse. Jennifer Coolidge guest starred as the inauthentically posh Amanda, an older friend who Phoebe and Monica try to "cut out." Amanda reveals that Phoebe once tried to cut out Monica, resulting in a fight. Coolidge's fake British accent deliciously adds to the few scenes she inhabits.

Season 7, Episode 13: The One Where Rosita Dies

Phoebe takes a job as a telemarketer, and her first call is with Jason Alexander's character, a man who plans on killing himself. Feeling semi-responsible and newly attached, Phoebe tries to convince him otherwise.

Seasons 9 and 10

Paul Rudd, aka Mike Hannigan, was first introduced as a random blind date for Phoebe. Mike later marries her - after an 18 episode stint throughout the series - claiming in his vows that she is "so wonderfully weird".

Seasons 2, 3, 5, 6, and 9

With a mustache so prominent that it made Chandler feel inferior, Tom Selleck guest starred as Dr. Richard Burke for 10 episodes on Friends. Richard was originally friends with Jack and Judy Gellar (Ross and Monica's parents), but he ultimately became lovers with Monica (his "chippie in the city"). Richard, already a father and grandfather, didn't want to have children, though, so he and Monica split.