VIDEO: Justin Bieber Surprises 'Friends' Fans on Show's Set and Hilariously Sings 'Smelly Cat'

Who wouldn't want to get serenaded by the Biebs? And how about on the set of Friends? A few lucky Friends fans just experienced a very intimate performance by none other than Justin Bieber. But here's the catch: Most of them had no idea it was him.

As reported by Rolling Stone, Justin went undercover as a Warner Bros. tour guide during an appearance on The Ellen DeGeneres Show. And he really got into character, interacting with tourists as they stopped by Central Perk on the Friends set. The disguise (which included a wig, glasses, and sideburns) is top notch, but as you might've guessed, some of those die-hard Beliebers were able to spot the superstar instantly.

The video is full of some hilarious moments for sure. At one point, Justin claims that the famous coffee shop couch has never been washed. He proceeds to unearth what very well could be 10 seasons worth of dust from its cushions. The true must-see moment is when he finally puts on the concert of a lifetime, performing a hilarious rendition of Phoebe's hit song, "Smelly Cat."

The best part? The fans join right in and they all sing the timeless classic together. Check out all the fun (and Justin's acting skills) in the clip above.