With a lot of Dark Souls bodies, you can explain it away with, "Well, someone died here!" But when one thinks about the corpses that show up with armor after you accomplish some task, it begs the question of how it gets there.
Take King Jeremiah's armor for example. I've walked by the Half-Breed before without there being a body; but now that I've killed Jeremiah's phantom,there's suddenly a corpse hanging out on one of the benches carrying his armor, complete with oddly-phallic helmet.
The same things happens with Lautrec, Kirk, Leeroy, and a few more I may be missing. Spontaneous Corpse Appearance happens quite frequently in this game, and I CAN'T be the only one wondering how/why it does. :x