Justin Bieber thrilled fans on Sunday night (24Jul11) by staging an impromptu performance at a concert by his girlfriend Selena Gomez.
Disney star Gomez played a gig at the OC Fair in Costa Mesa, California and the audience was stunned when she was joined onstage by Bieber midway through the show.
The Baby hitmaker gave Gomez a hug before launching into a medley of songs including his track Favourite Girl and the Justin Timberlake hit Cry Me A River, according to MTV.co.uk.
After the show, he took to Twitter.com to thank fans for their support before sending a message to Gomez telling her: "U did great tonight. Proud of u."

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