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Who knew Justin Bieber was such a "Friends" fan?

Matthew Perry is in on the 16-year-old singer's surprising little secret.

"I found out that [Justin], when he checks into a hotel -- we all use fake names -- he uses Chandler Bing," revealed Perry, whose "Mr. Sunshine" debuts on ABC this week-- on Tuesday's "Ellen DeGeneres" show.

"Well, now people know," DeGeneres cracked.

"Yeah," Perry retorted. "Gotta find a new one, pal!"

The TV vet wouldn't reveal what his own fake check-in name is -- but it sure isn't Justin Bieber. "Yeah, I would never. That's the worst name I could use!"

More on Wonderwall:

Willow Smith on Bieber: 'I Don't Have a Crush on Him'

Jen Aniston secretly hated her 'Friends' 'do

Bieber & Selena Gomez stage a hand-holding photo op

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