You're sans

Your brother wants to be in the royal guard extremely bad. You're both new to the underground. You barely remember where you come from. Papyrus was at the door of Undyne's all night. You just sat in a pile of trash and watched him. Undyne accepted him finally for "cooking lessons". Her reasoning was because every royal guardsman needed to be a good cook. After she sent Papyrus home, you went to talk to her.

You knocked on the door. She opened it

Undyne says," What."