So apparently the Undertale patch basically confirmed that Papyrus has the ability to use Gaster Blasters too. And also that he chooses not to use them against you and therefore Sans just like, took his...as soon as you seem to be going down the No Mercy Route. FOR POTENTIAL FUTURE USE.
(I’m basically assuming this is what happened, since in the patch if you halt a No Mercy run at Papyrus and goes to his room he is all like “oh hey my unused attacks i could have blasted you but.... Wait where did those go.)
Golly, Sans.
(I’m totally Sans in this scenario though, I would totally prepare way in advance to collect as many weapons against the murder child as possible I would totally sneak into my brother’s room and take his murder weapons he will never use. I understand Sans, we are both not pure in our souls like Papyrus.)
ALSO CONFIRMATION FOR SANS USING SOMETHING OF PAPYRUS’S TO KILL YOU WITH WHICH FULFILLS ALL THE “USE YOUR FALLEN LOVED ONES WEAPONS” TROPES I LOVE? AND WHAT MAKES IT EVEN BETTER IS SANS KNOWS PAPYRUS SPECIFICALLY WOULD NOT HAVE USED THIS WEAPON SO BY DOING THIS HE’S DISAPPOINTING HIS BROTHER??? IT’S SO HORRIBLE AND ANGSTY I LOVE IT.