Who knew these two were crazy in love with Britney Spears?! Beyoncé and Jay Z kicked off their weekend by traveling to Planet Hollywood Resort & Casino in Las Vegas to attend Spears' headlining residency show. As soon as Spears took to the stage, Beyoncé was spotted singing along to several songs and having a great time from her VIP seats. "She sang the classics like ?Baby One More Time,' ?Oops! I Did It Again' and ?Stronger,'" our eyewitness shared. "She seemed very excited to hear ?Me Against the Music' too. She was definitely happy to be at the show."