Was down in my mines, had blocked off a small area that has a spider spawner in it using wood blocks and fences. While near the barricade, saw 4 skeletons show up and walk toward the barricade and just stand in front of it. Then a couple of spiders spawned... On of them after while attacked one of the skeletons which caused the skeletons to fire in mass on the lone spider. Eventually all of the skeletons were dead but it was still fun to watch.