Fluffy

 are two Radroaches in the Abandoned Shack where you can get the Victory Rifle. They are caged, but you can open it to let them out. They will be hostile to the player. If you want to keep them alive in the cage don’t go in with Fawkes or Dogmeat, as they will kill them. If you get too close to the cage, they can still attack you and deal damage.