When You Become Frisk (当你变成了Frisk时) is a short comic with fan service which describes a fan of Undertale enters the game one day as Frisk. This comic have a similar story, despite that Frisk is actually a fan who has already known the detailed story of Undertale. Because of this, Frisk acts like she is breaking the Fourth-Wall such as her saying "Today isn't Sunday and I don't go to school.". Frisk chooses Pacifist Route (Although the author has drawn the extra Genocide Route Comic). Also, some characters especially Frisk uses memes (Mainly Chinese style memes) about Undertale. What's more, some expressions are based on animes such as Frisk's making her mouth water when meeting Papyrus.
Frisk is a girl who fell into the Underground. She is a supporter of Sans X Frisk and other shipping. She can't help exposing her love for Monsters and flirting them, especially with Sans.
As his appearance in Undertale, Flowey is waiting to give Frisk his "friendliness pellets". However, Frisk knows who he is and hugs him before Flowey can even start a conversation.
As his appearance in Undertale, Sans is a lazy skeleton and Papyrus' elder brother. He seems patient about Frisk's great enthusiasm on him. However, he notices something unusual in this Frisk.
Just like his appearance in Undertale, Papyrus is a energetic skeleton and Sans' younger brother. He is impressed by Frisk's enthusiasm and gives up on fighting her.