Yo I'm starting to think that Pap may have a teensy bit of Determination like Undyne and Sans. If you kill him, his body disappears instantly but /his head doesn't until much later/. He stays alive as a head to give you several last sentences before he dies for real. Now, he's not the only other monster who sticks around after being drained to 0HP (see Toriel & Asgore), but it's strange that he stays conscious even after most his body has been turned to dust. idek about this but... (pt.1)
(pt.2) what if the reason that's the case is because after The Incident, he became so full of despair that he fell down? Sans, utterly distraught and desperate, refused to let this be his baby bro's final fate. So he took him to Alphys. He stayed by his side as his lifeless body was injected with just the right amount of Determination. And turns out those experiments amounted to something beneficial after all, because Papyrus became the first and last completely successful "resurrection".
*Wheezes* PAPYRUS HATING HIMSELF SO MUCH THAT HE FALLS DOWN, WHY WOULD YOU SUGGEST SUCH A THING
M Y HEA RT













