Madonna startled an audience of tens of thousands by snogging rapper Drake in an unexpected climax to the Coachella music festival. The pop superstar was not due to appear at the three-day festival in the California desert, but walked on stage on Sunday night as Drake performed a song named after her.Madonna performed two of her own songs, including Human Nature, before bending over a seated Drake for a prolonged, full-mouth kiss.But the stunt didn't go to plan.Video of the encounter soon went viral and Drake's reaction - coming up for air and looking as if he was about to be sick - caught everyone's attention."Bitch, I'm Madonna!" she declared as she walked off.It was not the only sensual scene at Coachella, which is as renowned for skimpy clothing in the desert heat as it is for its trend-setting music.Among the emerging artists at Coachella was Danish electro-pop singer Mo, who delivered an impassioned set in which she twice went crowd-surfing, and the Welsh-born pop singer Marina and the Diamonds, who had a crowd singing along to her song How to be a Heartbreaker.Belgian singer Stromae, a sensation in the French-speaking world, delivered a riveting performance of his danceable, yet intelligent, pop tunes...