How did Niall Horan become an old man overnight? How did seksi Harry Styles transform into a nerd?
One Direction's amazing Best Song Ever video wasn't just record-breaking! It was mind-bending!
Ch-ch-check out the video (above) to go behind the scenes of one of the craziest videos of all time and see just how tough it was for the boys to tackle their roles!
Tags: behind the scenes, best song ever, harry styles, music minute, music video, niall horan, one direction