This is absolutely INSANE! Apparently when Taylor shot the video for "End Game" none of the dancers could even hear the song!! They performed to what's called a "Click Track" to help them stay on-beat while Taylor wore tiny headphones so she could hear and sing along. Apparently she did this to avoid any leaks of her as yet unreleased music. DAMN!!! That's some major security right there!!!!!!
Watch the video below to actually see some of the dancers trying to perform to the "Click Track!"