""LET THE PUZZLE BEGIN!""
(When Papyrus' Puzzle is Ready.)
Horror!Papyrus is the brother of Horror!Sans. He still enjoys spaghetti and puzzles. He is still like his brother, who wishes to end humans. He has his teeth sticking out, and has blood on his body, but he still wears the same outfit.
Horror!Papyrus still likes spaghetti. Even though he has blood on his teeth, Papyrus is still kind. For example: When you click the 'Insult' button during a cutscene of Aliza eating spaghetti, instead of killing you for disliking his spaghetti, he will say that he served it 'wrong'. He is the only monster with a sense of morality, and other monsters idolize him for it.
Horror!Papyrus is still the same original, kind, friend, puzzle lover. However, his appearance started to change after a 'Neutral Run' of Undyne being a queen. When he first met Aliza, instead of doing violent things, he asked Aliza if they were hungry.
Papyrus still wears his "Battle Body". Only his eyes and jaw are different. His teeth are narrow and covered with blood. His eyes are a lot smaller and rounder.
Horror!Papyrus cares about Horror!Sans, because they're brothers. However, if Sans ever does kill Aliza, it makes Papyrus a bit mad.
When Papyrus first met Aliza, he just asked Aliza if she wanted spaghetti. Papyrus doesn't mind if Aliza denies, When Aliza accepts their spaghetti, Papyrus is happy. (spaghetti is human flesh.)