Some A-list celebrities who made guest appearances on 'Friends' include Brad Pitt and Bruce Willis.

The show 'Friends' featured numerous guest stars in amusing plotlines.

The popular sitcom "Friends" ran for 10 seasons from 1994 to 2004, featuring an impressive cast including Jennifer Aniston, Lisa Kudrow, David Schwimmer, Courteney Cox, Matt LeBlanc, and the late Matthew Perry.

Some guest stars on the show, including Paul Rudd, Elliott Gould, Tom Selleck, Jon Favreau, Cole Sprouse, Aisha Tyler, and Anna Faris, had longer runs, while others had shorter but still memorable appearances.

25 Forgotten "Friends" Guest Stars

In the episode "The One After the Super Bowl: Part 2," Susie, an actress and former classmate of Chandler's, was portrayed by Julia Roberts as a guest star.

Chandler recounts an embarrassing moment he put Susie through in grade school, which they both laugh off, making it seem like she has moved on.

Susie appears to invite Chandler on a date, but secretly harbors ulterior motives.

In two "Friends" episodes, Amy, one of Rachel's sisters, is portrayed by Christina Applegate.

Rachel's sister, Applegate, was portrayed as a snobbish sibling in two episodes of "Friends": "The One with Rachel's Other Sister" and "The One Where Rachel's Sister Babysits."

In "The One with Rachel's Sister," Reese Witherspoon portrays Jill, Rachel's sister.

After the breakdown of his relationship with Rachel, Jill eventually has a fling with Ross.

Billy Crystal and Robin Williams' guest appearances on "Friends" were a result of happenstance.

According to Screenrant, Crystal and Williams were in the area during the filming of "The One with the Ultimate Fighting Champion." The writers asked if they wanted to be in a scene, and they agreed.

In the first scene of the episode set in Central Perk, Crystal and Williams were present. While Monica started narrating a tale, the dialogue between them was spontaneous.

Crystal's character is revealed to be the man Williams' character's wife has been sleeping with, causing the two to storm out of the coffee house in shock.

In the "Friends" episode where Dakota Fanning guest starred, she played a young child.

Mackenzie, a young girl, resides in the house that Monica and Chandler are relocating to.

In the episode "The One with Princess Consuela," Monica and Chandler take Joey to their new home, but at the time, Joey is struggling with the couple's move out of the city.

Joey discovers Mackenzie, who is upset about leaving the house.

In the episode "The One with the Cheap Wedding Dress," Gabrielle Union portrays the character of Kristen Lang.

As Monica, Phoebe, and Rachel battle other shoppers for a discounted wedding dress, a separate story unfolds involving Joey, Ross, and Kristen.

Joey and Ross, who live in the same neighborhood as Kristen, ask her out at different times.

In a hilarious dating battle, they decide to let her choose who she wants to be with once they find out they are going out with the same women.

In "The One with Monica and Chandler's Wedding: Part 1," Joey is starring in a film alongside the renowned actor Richard Crosby, portrayed by Gary Oldman.

The actor employs unique acting methods, such as forcefully spitting out his words.

In "The One with Monica and Chandler's Wedding: Part 2," the oldman almost makes Joey miss the wedding when he shows up drunk.

In an episode of "The One with the Rumor," Brad Pitt makes a guest appearance during the Thanksgiving celebration.

Monica extends an invitation to her former classmate Will, who is spending the holiday in the city without any plans, to join her for dinner.

In this episode, a high school secret and a rumor about Rachel that Ross and Will spread are revealed.

In "The One with Rachel's Big Kiss," Winona Ryder portrays a former sorority sister of Rachel's.

Rachel divulges to the group that she and Melissa (Ryder) shared a kiss in college, a claim that Phoebe vehemently denies as authentic.

The actress's appearance in "Friends" has been seen as a plot hole by many fans, as she was previously mentioned in a prior episode.

In "The One with Two Parts: Part 2," George Clooney and Noah Wyle portray medical professionals.

In this episode, Rachel proposes going on a double date with the doctors, but Monica refuses because she was secretly dating Chandler at the time.

Numerous actors have portrayed Phoebe's romantic interest prior to her wedding to Hannigan, including Paul Rudd.

One of the boyfriends in "The One with the Chicken Pox" is Ryan, portrayed by Charlie Sheen.

In the episode "The One with Ross's Tan," Jennifer Coolidge portrays Amanda Buffamonteezi, a former friend of Phoebe and Monica's who is known for being obnoxious.

She attempts to arrange a meeting with Phoebe and Monica, but they come up with various excuses, until they eventually run out of reasons.

Some "Friends" fans have been perplexed by Bruce Willis' repeated appearances on the show, as he is mentioned before actually appearing as a guest.

In several "Friends" episodes, the "Die Hard" franchise starring Willis is cited as a favorite movie of characters Ross, Chandler, and Joey.

In the episode "The One Where They're Up All Night," Chandler discusses "Armageddon" with Monica while in bed, another film featuring the renowned actor.

In three "Friends" episodes, Willis portrays Paul Stevens, the father of Elizabeth, who is Ross's much younger girlfriend.

At Phoebe's bridal shower, the elegant event takes a turn when the girls discover that Phoebe wanted a stripper. This is where Danny DeVito enters the scene.

In this episode, Ellen Pompeo plays Missy Goldberg, a former college crush of both Chandler and Ross.

Ross and Rachel's baby, Emma, is cared for by Freddie Prinze Jr., who portrays an overly sensitive nanny.

In the episode "The One with the Male Nanny," he portrays the character of Sandy.

Chandler is in Oklahoma for the holidays, far from his friends in NYC.

In the Christmas episode, Wendy, portrayed by Selma Blair, is present in the office alongside Chandler.

In three episodes of "Friends," Bonnie, played by Christine Taylor, dates Ross. The main episode she is in is titled "The One at the Beach," and she also has appearances in "The One with the Ultimate Fighting Champion" and "The One with the Jellyfish."

In the episode "The One with the Birth," Leah Remini briefly appears. The central plot of this episode revolves around Carol and Ross welcoming their newborn baby.

At the hospital, Joey encounters Lydia (Remini), a woman about to become a single mother. When Lydia goes into labor, Joey steps in to guide her through the birth.

In the episode "The One with the Screamer," Ben Stiller portrays the character of Tommy.

In an attempt to make Ross jealous, Rachel briefly dates Tommy in the episode. Tommy is known for frequently yelling.

In "The One After the Super Bowl: Part 1," Joey portrays Dr. Drake Ramoray, while Brooke Shields plays Erika, a fanatical admirer of Dr. Ramoray's character on "Days of Our Lives."

Throughout this episode, Erika cannot decipher reality from TV fiction.

In the episode "The One with the Halloween Party," Ursula's fiancé is portrayed by Sean Penn.

Ursula lied about her identity, causing Penn to break things off with her. Later, he dates Phoebe for a brief period.

John Stamos appears in an awkward dinner conversation with Monica and Chandler.

In the episode "The One with the Donor," Chandler's co-worker Zack is portrayed by Stamos.

Monica and Chandler, unable to have children of their own, explore the possibility of using a sperm donor. This leads them to question Zack over dinner about his potential suitability as a donor.

In "The One with the Tea Leaves" and "The One In Massapequa," Phoebe's boyfriend is portrayed by Alec Baldwin, who is known for his overly optimistic outlook on life.

He usually spends time in "The One In Massapequa," attending an anniversary party for Ross and Monica's parents with his friends.

In three episodes of "Friends," Dermot Mulroney portrays Gavin Mitchell, a character who assumes Rachel's work duties during her maternity leave.

While they begin as rivals, their relationship very briefly turns romantic.

In "The One with the Mugging," Jeff Goldblum portrays Leonard Hayes, a director who evaluates Joey's acting skills.