24 Friends Guest Stars You Might Have Forgotten About

In season eight, Brad Pitt shows up as Will Colbert, an old high school acquaintance of Rachel's and Monica's and fellow member of the I Hate Rachel Green Club with Ross.

Julia Roberts makes an appearance in season two as Susie Moss, someone Chandler knew in school and teased relentlessly. He asks her out, and she exacts her revenge by asking him to put on her underwear. Payback!

Christina Applegate plays one of Rachel's sisters, Amy, in seasons nine and 10. She's the one who pierces Emma's ears and insists on calling her Ella. Applegate even won an Emmy for this role!

Ben Stiller plays Tommy in season three's episode "The One With the Screamer," and you guessed it, Tommy is the screamer who Rachel goes on a date with.

Parker, Alec Baldwin's character who goes on a few dates with Phoebe, appears in season eight. Who could forget his blatant enthusiasm for life and his need to take mental pictures of everyone. Click!

Reese Witherspoon famously plays Rachel's other sister, Jill, in season six. She tries to get a little too chummy with Ross, which obviously doesn't fly with Rachel.

Dermot Mulroney guest stars as Rachel's boss Gavin Mitchell in season nine and low-key throws a wrench in the Ross-and-Rachel love story.

In season seven, Winona Ryder appears as Melissa Warburton, one of Rachel's old college friends who has been harboring a crush on her for years.

Charlie Sheen plays Phoebe's US Navy lover who has returned from sea to reunite with her and doesn't even care that she's plagued with chicken pox.

Of course Ralph Lauren makes an appearance as himself in season six. Rachel does work for him, after all.

Christine Taylor plays Ross's girlfriend Bonnie in season four. Rachel totally tricks her into shaving her head, and she ultimately gets the boot when Rachel decides she wants another chance with Ross.

As actor Richard Crosby, Gary Oldman guest stars alongside Joey in a movie he's filming about soldiers in WWI.

Bruce Willis plays Paul Stevens, the dad to Ross's young girlfriend and casual love interest to Rachel, which makes for some interesting situations in season six. He also won an Emmy for this guest-starring role.

In season nine, Jeff Goldblum makes a guest appearance as director Leonard Hayes, whom Joey is auditioning for.

These two make a quick and funny cameo in season three as Tim and Tomas in Central Perk.

Jon Lovitz guest stars as Steve in both seasons one and nine. As Steve in season one, he's a restaurant owner whom Monica invites to try her food and he shows up high. As season nine's Steve, he goes on a blind date with Rachel that doesn't exactly go well.

Ellen Pompeo has a guest spot as Missy Goldberg in season 10. She's an old acquaintance of Ross and Chandler from college, and they see her again at their reunion.

Helen Hunt plays Jamie Buchman in season one for a short bit mistaking Phoebe for her sister, Ursula.

Anna Faris's guest role was a handful of episodes in season 10 as Erica, the pregnant woman who gives Chandler and Monica her babies.

Who could forget Jennifer Coolidge as Monica and Rachel's old friend Amanda Buffamonteezi in season 10? She's adopts a fake British accent and constantly talks about her mobile phone.

The E.R. doctors guest star in season one as doctors yet again.

Sean Penn plays Ursula's fiancé, Eric, in season eight and even tries dating Phoebe for a hot second.