Justin Bieber is GaGa’s closest rival; he has 8.3 million fans on Twitter and is expected to hit the nine million mark in the coming weeks. Britney Spears is currently the third most popular person on the social networking site, followed by Barack Obama and Kim Kardashian, who has a healthy 6.9 million followers.

Lady GaGa isn’t resting on her laurels – she treated lucky fans in Las Vegas to a surprise gig on Friday 25 March. The chart-topper took to the stage at Krave nightclub in Planet Hollywood and sang Born This Way for the capacity crowd while dressed in a leather jacket, sheer bodysuit and black thong.

She was in town for Saturday night’s concert on her never-ending Monster Ball Tour. During the show, at MGM Grand Hotel and Casino, fans sang Happy Birthday to the stunned star, who turns 25 on Monday.