Simple concept that I and I assume many others had about Papyrus if the game allowed sans to be kills first. Having phase 1 of the fight involving him labeled as "Mysterious Royal Guard" where attacking him would just damage his helmet and a shield that would come up when you swing. And phase 2 revealing who it actually is (even though its obvious) along with him picking up the pace of the fight and still would use the shield to block all damage. He is wearing the coat of his brother along with wielding the spear of Undyne. Figured it'd be neat for him to be a boss that would fight using Sans' and Undyne's attacks. With the only true way to win is to wait until he gets to a certain point where he seems sad and try and die to his attacks. He would let his guard down when hesitant to continue fighting which would allow you to cutabitch