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Tom Selleck -

Now that we know Monica and Chandler end up together, it's easy to forget that in the beginning there was Richard. The handsome, much older dentist is played by none other than Tom Selleck, who's also set to appear in the reunion special.

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Kristin Davis - The 'Sex and the City' star made a short but sweet appearance in season 7. She featured in one episode, and her character was Erin, a date of Joey's who is a hit with Rachel and Phoebe.

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Bruce Willis -

Bruce Willis definitely gave one of the more memorable guest appearances on the show. In season 6, he plays Paul Stevens, the disapproving father of Ross' much younger girlfriend.

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Jean-Claude Van Damme -

Jean-Claude Van Damme played himself in the most-watched episode of all time–'The One After the Superbowl' (season 2). The episode originally aired on January 28, 1996.

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Richard Branson -

Richard Branson famously made a cameo appearance in 'The One With Ross' Wedding.' When the gang travel to London for the party, Branson is there selling souvenirs on the street.

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Sarah, Duchess of York - Sarah, Duchess of York, who is popularly known as Fergie, appeared as herself to take a 'selfie' with Joey, also in 'The One With Ross' Wedding' (season 4, episode 23).

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Michael Rapaport -

Michael Rapaport featured in four episodes as Gary, Phoebe's cop boyfriend. At one point he takes the boys on a ride along and they freak out when a car backfires.

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Elle Macpherson -

Joey and Janine (Elle Macpherson) start out as roommates. They try to have a romantic relationship, but it doesn't work out because she can't get along with Monica and Chandler.

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Charlie Sheen -

Phoebe gets a stroke of bad luck in season 2 episode 23 when her Navy beau (Ryan, played by Charlie Sheen) returns to find her riddled with chicken pox.

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Jason Alexander -

In 'The One Where Rosita Dies,' Jason Alexander plays Earl, a depressed office worker to whom Phoebe tries to sell toner. She ends up bringing him back from the brink of taking his own life.

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Julia Roberts -

Julia Roberts featured in a single episode in season 2. She played Susie Moss, Chandler's childhood friend who returns to get revenge on him for a prank he played years ago. Late actor Matthew Perry and actress Roberts famously started dating after her appearance.

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George Clooney -

George Clooney appeared alongside Noah Wyle in season 1 episode 'The One With Two Parts: Part 2.' He played an ER doctor who looked after Rachel after she sprained her ankle.

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Tate Donovan -

Tate Donovan's character Joshua featured in a number of season 4 episodes. He played Rachel's love interest, which was ironic since Donovan had recently broken up with Aniston in real life.

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Winona Ryder -

Winona Ryder put in an appearance during season 7. She played Melissa Warburton, Rachel's college friend with whom she claimed to have shared a drunken kiss.

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Brad Pitt -

Brad Pitt appeared in a season 8 episode as Will Colbert, an old friend of Ross' and former president of the I Hate Rachel Club. He was, of course married, to Jennifer Aniston at the time.

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Anna Faris - In one of the saddest episodes, Monica and Chandler find out they can't have children. They decide to adopt. Who should be their adoptive mother? None other than Anna Faris!

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Christina Applegate - Rachel is one of three kids and both her sisters feature at one point or another over the course of the show. Her nightmare sister, Amy, is played by Christina Applegate. Her youngest sister, Jill, is played by Reese Witherspoon.

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Marlo Thomas - On the topic of Rachel's family, who can forget the guest star appearance of Marlo Thomas as Rachel's mother? She appears in a total of three episodes, two in season 2 and one in season 8.

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Sean Penn - Phoebe also has a sister with whom she doesn't get a long. That sister's name is Ursula, and she crops up at various points. At one point she has her fiancé, Sean Penn, in tow.

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Greg Kinnear - When Ross starts to date beautiful fellow nerd Charlie (Aisha Tyler), all goes swimmingly for a while. That is until he comes across Charlie's crazy ex, Dr. Benjamin Hobert (Greg Kinnear).

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Danny DeVito - Who could forget Danny DeVito as the has-been stripper whom Monica and Rachel invite to Phoebe's bachelorette party?

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Alec Baldwin -

Towards the end of season 8, Alec Baldwin plays Phoebe's sweet but infuriatingly overenthusiastic boyfriend, Parker.

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Teri Garr -

Teri Garr appeared in a total of three 'Friends' episodes. In 'The One At The Beach,' her character, Phoebe Abbott, reveals to main Phoebe that she's her birth mother.

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Paul Rudd - Paul Rudd joined the show in season 9 and quickly became a familiar face. His character, Mike, starts out as Phoebe's blind date and ends up as her loving husband.

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Cole Sprouse - Who could forget Cole Sprouse's adorable performance as Ben, Ross' son from his first marriage? Sprouse portrayed Ben in seven episodes across seasons 7 and 8.

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Elliott Gould and Christina Pickles -

Elliott Gould and Christina Pickles featured in a number of episodes across the years. Whenever they did, Jack and Judy simply stole the show.

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Jane Sibbett -

Jane Sibbett played the second Carol Willick, ex-wife to Ross and mother to their son, Ben. The original Carol was played by Anita Barone, but she was replaced after one episode.

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Helen Baxendale -

Helen Baxendale stars in a number of episodes as Ross's second wife, Emily, whom he embarrasses at the altar when he calls her by the wrong name.

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Eddie Cahill -

Eddie Cahill was another returning guest star who played a love interest of Rachel's. She initially hired him as her assistant, and then the pair went on to date.

Sources: (Bustle) (Gold Derby)

See also: How Jennifer Aniston escaped the 'Friends' curse

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