20 Best 'Friends' Cameos of All Time: Brad Pitt, Julia Roberts, Bruce Willis and More

Ben Stiller appeared on Season 3 of Friends after Jennifer Aniston's Rachel and Matthew Perry's Chandler split. Stiller played the role of Tommy, Rachel's new man known for his short temper.

On Season 5 of the hit sitcom, Bob Balaban starred as the deadbeat father of Phoebe, Lisa Kudrow's character. He showed up during the funeral of Phoebe's grandmother.

Brad Pitt came onto the show as Will Colbert, an old friend of Rachel, Ross (David Schwimmer) and Monica (Courteney Cox). He shocked everyone when he admitted to being a member of the "I Hate Rachel Green Club" in high school.

Pitt's appearance earned him a nomination for the Outstanding Guest Actor In A Comedy Series at the 2002 Emmy Awards.

Starring as Paul Stevens, Bruce Willis appeared in three Season 6 episodes of Friends. He portrayed the role of the father of Ross' girlfriend — a college student.

After the appearance, Perry revealed that Willis agreed to appear on Friends after losing a bet over whether their film, The Whole Nine Yards, would be a hit. The 2000 film ended up scoring $106.4 million at the box office.

Willis later won the Outstanding Guest Actor In A Comedy Series at the 2000 Emmy Awards.

Christina Applegate starred as a guest on several episodes of Friends. She played the role of Rachel's insensitive sister, Amy.

Applegate won the Outstanding Guest Actress In A Comedy Series at the 2003 Emmy Awards after her appearance.

Danny DeVito also earned a nomination for the 2004 Outstanding Guest Actor In A Comedy Series at the Emmy Awards for his role as Roy. He hilariously appeared as a stripper who got hired for Phoebe's bachelorette party.

In an episode from Season 7, Gabrielle Union briefly appeared as Kristen. She won Joey and Ross' attention, leading her to go on dates with both of them.

Although Union was one of the most notable guest stars in Friends, she told Black Film what she felt when she joined the show.

"But as far as Friends, I think I was kinda the guinea pig just so the NAACP doesn't picket in front of the studio. But lucky Aisha [Tyler] got to step in and kinda pick up. As long as there are people of color. It just needs to be a little more diverse," she told the outlet.

Gary Oldman showed his acting skills as Richard Crosby, a famous actor who worked with Joey (Matt LeBlanc) in a film about World War I soldiers.

Oldman also got an Emmy nomination for Outstanding Guest Actor In A Comedy Series in 2001 for his portrayal.

Jeff Goldblum transformed into a theater director named Leonard Hayes in a Season 9 episode of Friends. He initially clashed with Joey, but they later got along.

Julia Roberts was Chandler's former classmate in the sitcom. Playing the role of Susie, she and Chandler went on a date.

However, it was only part of her plan to get revenge on him after he teased and flashed her when they were still in school.

Kathleen Turner shocked viewers when she appeared on Friends as Chandler's trans father. In the sitcom, she became a Las Vegas-based drag show performer who went by the name Helena Handbasket.

Paul Rudd appeared on Friends as Mike Hannigan, Phoebe's boyfriend and later husband. According to the Ant-Man actor, the experience was "strange" and "surreal" after spending time with the cast.

During Season 4 of Friends, Rebecca Romijn appeared as a Ph.D candidate who started dating Ross.

In an interview after the gig, she revealed that it was her first paid acting job.

"I was just modeling at the time I got that show. [Being] my first professional acting job, I was scared shitless! And it was amazing!" said Romijn.

She added, "I was so nervous as it was really at the height of the success of that show. I wasn't such a name at that point. I guess I was working for Sports Illustrated and had been working with Victoria's Secret, so I don't know that I wasn't a name, but I hadn't acted. Although, I did grow up in musical theater as a kid, so it wasn't like I'd never acted. I had been since birth."

Reese Witherspoon played the role of Jill — Rachel and Amy's sibling — in several episodes of Friends. She even teased Rachel and made her jealous by getting closer to Ross.

Starring as Eric, had to choose between the Buffay twins in an episode of Friends.

Episode Director Kevin S. Bright told Metro U.K. in 2018 how Penn performed at the time.

"I think the least successful one was [Sean] Penn on the show," Bright said of Penn's difficulties when he transitioned from being a movie actor to a TV star. "Just the style of the production wasn't what he was used to, doing a show like that, so there was a little deer in the headlight effect."

Selma Blair appeared as Wendy, who stayed at the office when Chandler was forced to work on Christmas. The character was having marriage issues at the time, and she wanted to have an extramarital Christmas treat to complete her holidays.

Susan Sarandon played Jessica's character, Joey's costar on Days of Our Lives, in Season 7. Jessica and Joey hooked up after it was revealed she would be killed off the show.

Tom Selleck joined Friends as a guest star when he played the role of Dr. Richard Burke. He appeared in 10 episodes as his character dated Monica.

Friends introduced Winona Ryder's character, Melissa Warburton, during a Season 7 episode. She was Rachel's friend from college, whom she kissed after drinking too much, though Melissa could not remember it. She later admitted to being in love with Rachel.