Britney Spears & Iggy Azalea Pretty Girl at Billboard Music Awards 2015

Britney Spears and Iggy Azalea's "Pretty Girls" collabo already gave us one of the summer's best music videos. And on Sunday night in Las Vegas, they delivered one of the most memorable performances at the 2015 Billboard Music Awards.The single is meant to promote Spears’s ongoing residency in that city, and the performance served as an apt advertisement for the pop star’s stage show: Spears, who’s performed on television rarely since her 2007 “Gimme More” fiasco at the MTV Video Music Awards, seemed both with-it and truly delighted to be onstage.While the event happened in the MGM Grand Garden Arena, the ladies performed their single “Pretty Girls” live from Britney‘s AXIS Theater at Planet Hollywood. This was the first time that Brit and Iggy have performed the song live together. Earlier in the night, they walked the red carpet together with their boyfriends.