They might be shocked. Since fanfiction can often deviate from the original plot, characters could be taken aback by unexpected storylines or characterizations.
There's also a possibility of confusion. Fanfictions sometimes introduce complex or convoluted ideas that might not align with the characters' own understanding of their world. So they could end up being really confused while reading it.
They might be amused. Since fanfiction often contains creative and sometimes humorous takes on the original story, characters could find it funny to see how fans imagine different scenarios for them.
They could also be confused. If the fanfiction takes a really wild turn from the original story, characters might not understand the new concepts or relationships presented. For example, if a fanfiction pairs two characters who have no interaction in the original in a romantic way, it could be bewildering for them.
They may also be confused. Fanfictions often take the original story in new directions, and characters might not understand why certain things are written the way they are. For example, if a fanfiction changes the relationship dynamics between characters, they could be left scratching their heads.
They might be amused. Some characters could find the creative interpretations in the fanfiction quite interesting and it might make them laugh or at least bring a smile to their faces.
Others might be critical. For example, if the fanfiction goes against the established canon of the Danny Phantom universe, they could be annoyed or feel that it misrepresents them. They might think that the author didn't do enough research on their personalities or the story's lore.
They may also be indifferent. There could be so much fanfiction out there that they just get used to it and don't really care what's written about them in those fictional works. It could be like just another part of the whole South Park phenomenon that they are part of.
Some characters might be amused. They could find the creative interpretations in the fanfiction quite entertaining and laugh at the funny or unexpected scenarios written by the fans.
They might be amused. Since fanfiction often takes the original story in new and unexpected directions, the characters could find the creative interpretations funny.
Some characters might be amused. They could find the creative interpretations in the fanfiction quite entertaining and enjoy seeing different takes on their own stories.
They might be amused. Some characters could find the creative interpretations in the fanfiction quite funny and enjoy seeing how fans view them in different scenarios.