What do you get when you mix Charli XCX, Halsey, and Lollapalooza? An incredible cover of Spice Girls' "Wannabe," that's what. The duo took the stage at Chicago's annual music festival on Sunday, where they surprised fans with a (fire) interpretation of the classic 1996 anthem. We realise Halsey and Charli XCX are both busy with their solo careers, but this song is proof that we need the two of them to form a girl group, ASAP (maybe CupcakKe can be the final member?). Grab some body glitter and the nearest tube of Lip Smackers, and then check out their cover above.