Board Thread:General Discussion/@comment-5413572-20160521065337/@comment-27701762-20160521083216

Why does this need a specific explanation, though? As we move around the Underground we see all types of monsters, including monsters that are basically anthropomorphized animals. We see demon-like creatures, blobs, creatures made of flame, dogs of varying stature, etc., etc., etc. And many of the creatures are vaguely or fairly human-shaped. Why is "humanoid skeleton" so out there, such that it needs a special explanation of how it came to be?

The main problem is that monster bodies are composed almost entirely of magic. Which is why their bodies disintegrate pretty much immediately. In observing Papyrus's death, his body disintegrates pretty much immediately, with the only exception being that his head survives for just a bit longer (though it too turns to dust). The same magical composition is why monster bodies cannot handle determination, and so why you get the Amalgamates and you observe Undyne melting away. Determination would destroy the body, not allow it to fuse: the "unbridled emotion" of Mad Dummy is not determination. In fact it is a sort of combination of disgust and anger, probably mostly anger.

At best you could posit the following: Papyrus and Sans are in fact ghost monsters that inhabited human skeletons and fused with them, consistent with the way Mad Dummy fuses with its body. But there is no evidence for this premise, and the only justification for even entertaining it is because humanoid skeletons are supposedly unique, which is true of nearly all the monsters types in the Underground. We need more to go on to justify the excursion.