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!"