Britney Spears is shocking fans and not only because she's sporting an impressive waistline in her latest dance video. The pop star made jaws drop when she posted footage showcasing herself twirling in the sunshine with an interesting song of choice: "Filthy" by her ex-boyfriend Justin Timberlake! Britney Spears even showed her former flame some love by calling him a "genius" and addressed their famous breakup in 2002 after dating for four years. Their split was riddled with cheating rumors, including one involving the "Toxic" singer's backup dancer.