The young stars are both faces of the jean and underwear brand and they flew into China together to show off their wares at a special event.

However, Bieber decided to give attendees a live mini-gig, belting out his hits One Time, Boyfriend and Beauty and a Beat, among others, at the request of one excited devotee.

His manager Scooter Braun took to Twitter.com to share the news with followers, writing, "Yeah @justinbieber is killin (sic) it at (the) #calvinkleinlive event in Hong Kong. Out of no where (sic) he took a request and is playing #onetime!"

The Hong Kong event was the latest unplanned Bieber performance after singing a cover of Boyz II Men's I'll Make Love to You during Jazz Night at the W Hollywood Hotel and playing an acoustic concert in a Los Angeles bowling alley last month (May15).