It's true, the cast of Friends was a pretty close-knit group for the best part of ten years. Yet, every once in a while, a vacancy or two would sprout up, and a little space would be made for a superstar to make a mark as a guest among the classic Friends roster.

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As time rolled on and its reputation evolved, the series embraced bigger and bigger names, with some being pulled directly from the Hollywood A-list. Let's face it, it didn't matter if they only dropped in to show their faces, or even if they grunted a single line and waltzed off. They would always leave a lasting impression. That said, which guest stars conjured the biggest reaction, and which of them stole the show just for being a local at Central Perk?

Charlie Sheen

Charlie Sheen in Friends

"The One With The Chicken Pox" was a fan favorite from the second season of Friends, and for good reason. Thanks to Charlie Sheen who, up until the episode being shot, was knocking about in movies such as The Rookie, Hot Shots!, and The Chase, the episode immediately struck a chord with audiences.

As an old love interest of Phoebe's (Lisa Kudrow), Ryan (Sheen) comes to visit after being granted leave from the Navy. However, when Phoebe comes down with chickenpox, the two are forced to either extinguish the flame or fight to rekindle the wick.

Bruce Willis

Bruce Willis on Friends

Prior to setting up shop as a regular at Central Perk, Bruce Willis was known for portraying some of the biggest action icons in the film industry. However, even with Friends being a kind-spirited sitcom with minimal serious tones, his character still resembled a lot of his old flames — Die Hard's John McClane included.

Contrary to what many believe about the Hollywood A-lister losing a bet with Matthew Perry and having to appear as a guest on the show as a forfeit, Willis did actually openly accept the role as one of Rachel's (Jennifer Aniston) season 6 love interests. Plus, his time on the show also spanned three episodes, making him one of the most familiar guests on the show.

Jeff Goldblum

Jeff Goldblum in Friends

One of the most heavenly voices of a generation thankfully dropped in to pay a visit in "The One With The Mugging." This season nine episode observed Joey's rise to fame, and Leonard Hayes' (Jeff Goldblum) struggle to mentor him for a new play.

Although his time on Friends was short, Goldblum still managed to make his screen time memorable, using his iconic tone and warming personality to (however briefly) upstage the show's frontrunners.

Winona Ryder

Winona Ryder in Friends

When we found out that Rachel had once shared a kiss with an old sorority roommate, we didn't expect it to be with Winona Ryder. Well, technically, it was with Melissa Warburton, but you know. The point is, we never expected the Beetlejuice star to set aside time for the Central Perk locals, but her appearance remains one of the most iconic.

After bumping into an old sorority sister (Ryder) in Central Perk, Rachel invites her to dinner, convinced that they both shared a kiss years prior. However, with both Phoebe refusing to believe the claim and Rachel's old flame struggling to recall it, Rachel looks to rekindle the spark as a way to prove it really happened.

Brad Pitt

Brad Pitt on Friends

Brad Pitt was without a doubt one of the most popular stars around the time Friends cast its eighth season. With Se7en, Fight Club, and Snatch already being under his belt, as well as Ocean's Eleven in the works, the A-lister was sure to turn a few heads when popping in for a one-off episode.

In "The One With The Rumor", Monica and Ross invite a friend to Thanksgiving, Will (Pitt). However, with a burning hatred for Rachel, the guest quickly becomes hostile when hearing that she's due to join them for the festivities.

Julia Roberts

Julia Roberts in Friends

Chandler Bing probably had one of the messiest relationship timelines in the show, flings and stalking stints included. However, nothing beat the time Susie Moss (Julie Roberts) came to town and filled a huge spot in his unorthodox portfolio of love interests.

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After finding out that an old classmate, now being a famous actress (Roberts) has come to town, Chandler looks to reunite with her for a catch-up, unaware that their rather shady history together would be regurgitated in the worst possible way.

Ben Stiller

Ben Stiller in Friends

Long before Ben Stiller cemented his name in the hall of Hollywood greats, he was tying up roles in flicks such as Disney's Heavyweights, Reality Bites, and Flirting with Disaster. Come 1997, and he made his Friends debut in the one-off episode "The One With The Screamer."

Learning of Ross's (David Schwimmer) new flame, Rachel makes a last-minute call to secure her own for a double date, unaware that Tommy (Stiller) is prone to lash out at the smallest of things. This includes screaming at theatre goers for sitting in the wrong seat.

Danny DeVito

Danny DeVito in Friends

One of the best sitcom scenes of all time still remains with Danny DeVito and his legendary striptease for Phoebe in Friends. Although only amounting to a few short minutes of screen time, his role as Roy was hands down one of the most memorable in all of the series.

As Officer Goodbody, the acclaimed comic took to the stage and performed an entire routine for Phoebe's bachelorette party in "The One Where The Stripper Cries." However, after the trio mocks the performance and his physicality, the veteran stripper begins to fear that his days in the spotlight are over.

George Clooney

George Clooney and Noah Wyle in Friends

For years, fans of the show loitered over the hopes of seeing the beloved George Clooney take time out of his busy schedule to swing by Central Perk for a quick cup of coffee. As luck would have it, he actually did in "The One With Two Parts."

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After Rachel falls from a balcony and sprains her ankle, Monica (Courtney Cox) looks to secure dates with two of the hospital employees, one being Dr. Michael Mitchell (Clooney) with his ER costar Noah Wyle at his side. However, being oblivious to their inappropriate actions, both Rachel and Monica, unfortunately, fail to woo the doctor duo and send them running for the hills.

Robin Williams

Robin Williams and Billy Crystal in Friends

Of course, it's Robin Williams, along with Billy Crystal, who also shared the set with the late comedy legend, that comes out on top. Even though the duo only shared the stage with the Friends cast for a single scene, it was still one of the most beloved moments from the ten seasons combined.

The scene had no real structure to it, funnily enough. Rather than being formally invited to the show, both Williams and Crystal just dropped in between filming scenes for Father's Day in a nearby studio. Although it was entirely unscripted, it was still the work of two legends coming together to make off-the-cuff comedy gold.

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