What is the story behind Joe Root's 'pinky finger' celebration against India?

England's Joe Root celebrated his Edgbaston Test hundred against India by wiggling his pinky finger. It was a reference to a scene from singer Elvis Presley's biopic 'Elvis'. In the movie, Elvis wiggles his little finger despite being ordered by police not to perform his signature movements. Root revealed Ben Stokes watched 'Elvis' and asked the team to be "rockstars".