Britney Spears celebrated her 27th birthday on Good Morning America with a performance of Womaniser and Circus from her new album, Circus, and was presented with a multi-storied Circus-themed cake by the show's host, Diane Sawyer. Both her sons were in the audience to watch their mum kick up a storm in a cabaret-themed costume and top hat. Despite attracting some criticism for miming the songs, Britney's skimpy costumes left no doubt she's made a physical return to form.