Camila Cabello and Shawn Mendes Perform 'I Know What You Did Last Summer' on Ellen: WatchCamila Cabello and Shawn Mendes Perform 'I Know What You Did Last Summer' on Ellen: WatchThe Fifth Harmony star and the 'Stitches' singer teamed up once again, this time on the stage of 'Ellen.'PopCrush StaffPopCrush Staff