Some characters might be amused. For example, Sans would probably make some witty remarks about the fanfiction's plot twists. Papyrus, on the other hand, might be a bit confused at first but then get really excited if he finds a heroic role for himself in the fanfiction.
There's no information available to me about the creators of '246 graphic novel'. It could be created by students in an art school as a project. They might have chosen the name '246 graphic novel' just for the sake of having a distinct title. Another possibility is that it's the work of an international team, where different members contributed to the story, art, and overall design, and the number 246 has some significance within their creative process that we are not aware of.
The main creators of comics typically include comic book writers who conceive the plot and characters, artists who do the illustrations, and in some cases, inkers and letterers. Different comics may have different combinations of these roles contributing to the final product.
In a comical fanfiction, most of the characters would enjoy it to some extent. Sans and Papyrus would be great additions to a comical story, and they would probably laugh along with the funny parts. Frisk, depending on how they are portrayed in the fanfiction, would either be the source of the comedy or be reacting to the absurd situations. In a more serious and political - themed fanfiction about the Underground's society, Asgore and Toriel would have deep thoughts. They might discuss among themselves how the fanfiction's view of their leadership and the society they built compares to their own intentions.
It adds variety. The undertale fandom is huge and diverse, and frans lemon fanfiction offers a different take on the characters and their relationships. It gives fans who are interested in this particular pairing more content to enjoy.
The creation of anime and manga involves various professionals. Writers come up with the storylines, illustrators draw the characters and scenes, and directors oversee the overall production. Some well-known names include Hayao Miyazaki and Akira Toriyama.
Manga creators typically own their series. But it can get complicated. Sometimes, they might have to share some rights with publishers or production companies depending on the contracts they sign.