'Friends' reunion guest star who left Lisa Kudrow shocked

Lisa Kudrow was as shocked as the rest of us when she heard about one celeb guest. Photo / Getty Images

It's one of the most highly anticipated returns in TV history, and now Lisa Kudrow has revealed which part of the hotly anticipated Friends reunion special left her "shocked".

The special, called Friends: The Reunion, reunites the stars of the hit show, however, they won't be appearing in character.

"It's completely unscripted. It's us seeing each other and they rebuilt the sets on [the show's original Warner Bros soundstage] Stage 24. It's done really well, too. But it's us, and also just cutting around – there are clips and things," Kudrow told the New York Post.

Kudrow shared that the cast will be viewing some video footage chronicling their time on the series that they hadn't seen before.

"It turns out [a crew member] was taking home movies that I didn't know about, and that was brilliant [to see]. There's so much great stuff."

"It was a lot of laughing and then real blubbering – which, I don't know if that will be in there, but the puffy eyes are in there, so that's good. It was an emotionally exhausting and great few days."

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Kudrow, who plays Phoebe Buffay, is also joined by Jennifer Aniston who played Rachel, Courteney Cox, who played Monica, Matt LeBlanc, who played Joey, Matthew Perry, who played Chandler, and David Schwimmer, who played Ross.

The actors will also be joined by a list of A-list stars like David Beckham, BTS, James Corden, Cara Delevingne, Lady Gaga, Kit Harington, Mindy Kaling, Reese Witherspoon and Malala Yousafzai.

"There's just a lot of surprises – like, things we weren't expecting," Kudrow told New York Post. "People showing up that we were surprised by. There's a lot going on in it."

But there was one guest that left Kudrow particularly speechless.

"I was like, 'Wait, that's Justin Bieber. Right? Would he be here? Is he here? He's really here; that's Justin Bieber!" said Kudrow. "That was kind of exciting. I'm throwing in a 'kind of' so that I seem a little cooler. It was exciting. I don't get excited about meeting people – but Justin Bieber, he's exciting."