On the updated version of Nuketown, unfortunately named Nuk3town in Call of Duty: Black Ops 3, you can once again unlock a special Easter egg with the mannequins. In the first Black Ops game, I believe you had to remove the head from each mannequin and it played a song throughout the map.

This time, you need to remove the arms from each of the mannequins in the updated Nuketown map. The result is them all turning into fast moving agents of death that only move when you aren't looking. They will sneak up behind you and beat you to death if you aren't careful. The first couple of minutes in the below video is just the guy shooting off mannequin arms, so you may want to skip ahead a bit.