Steven Tyler’s girlfriend is a Backstreet Boys fan! During each show the BSB give a lucky lady in the audience a rose while singing their song "Shape Of My Heart". On Friday night that lady just happened to be the girlfriend of Aerosmith’s lead singer, so he came out on stage and joined them. He tweeted out this video with this caption: "HEY I THOUGHT I WAS ONLY DOING 3 SHOWS A WEEK IN VEGAS. TOOK THIS ONE TO SEE THE @backstreetboys CONCERT MY WAY!"