Youtuber TheHiddenBlade01 discovered an interesting easter egg on the map, Nuketown. If you shoot all of the mannequin’s arms off in under two minutes, something really interesting happens.
If and when you do complete this, the music changes into something sinister. And while your back is turned from the mannequins, they’ll beat you to death. When you face forward, they freeze in their spot, and it’s reminiscent of the Doctor Who episode, Weeping Angels.