The Chainsmokers brought the house down as they closed our first ever #MonsterMashUp This image appears in the gallery:#MonsterMashUp 2016: ALL The Photos From Last Halloween's BIGGEST Party 53. The Chainsmokers brought the house down as they closed our first ever #MonsterMashUp (Pic: PA) 77 images See the full gallery: #MonsterMashUp 2016: ALL The Photos From Last Halloween's BIGGEST Party