They might be quite surprised. Some characters could be amused to see different interpretations of their stories in the fanfiction. For example, a heroic character might find it interesting to see how fans imagine their backstories in more detail or how they interact with other characters in new and creative ways.
They might be excited. In fanfiction, characters could be full of anticipation for the new storylines, new characters, and the overall development in Descendants 3. They might be discussing among themselves about the possible twists and turns.
Then there are those characters who might be inspired by the fanfic. They could see new possibilities for their own development. If the fanfic shows a character in a more complex or interesting way, it might give the real character ideas about how they could grow or change in their own 'Descendants 2' world.
They might be quite surprised. Some characters could find it strange to see their own stories being reimagined in different ways by fans. For example, if Sherlock Holmes were to watch elementary fanfiction, he might be intrigued by the new interpretations of his deductive reasoning skills or his relationships with other characters like Watson.
The characters might also feel a sense of flattery. If they see that the fanfiction writers are so passionate about their world and go to great lengths to create these stories. Kristoff, for instance, might be happy that fans are interested enough in his character to include him in different adventures in the fanfiction, even if those adventures are a bit far - fetched from his real - life (in - the - movie - life) experiences.
Well, some characters might be a bit critical. If the fanfiction strays too far from the essence of their personalities or the story of Encanto, they could be disappointed. Take Abuela, for instance. If a fanfiction shows her in a completely uncharacteristic way, she might not like it. Also, characters like Bruno might be amused to see how the fans imagine his hidden years and his relationship with the family in the fanfiction.
They might be surprised at how their actions are reimagined. For example, Iron Man could be astounded to see a version of himself in a situation he never thought of in the official storylines.
The characters might find it interesting to see different scenarios that the fans create for them. Maybe there are fanfictions that put them in completely different worlds or situations, like facing a new kind of dragon that doesn't exist in their own world. This could make them think about how they would actually react in such strange circumstances.
Well, they would probably have a range of reactions. Gwen might be more open - minded about it. She could see the fanfiction as a creative exploration of their world and the relationships within it. She might even enjoy seeing the different ways the writers develop her character, perhaps giving her more agency or different storylines than in the original show. As for Merlin himself, he might be a bit embarrassed at times, especially if the fanfiction delved into his secret magic in a very public or unusual way.
Some characters might be amused. For example, Bilbo himself might find it interesting to see different interpretations of his adventures. He could be entertained by how the fanfiction writers expand on his character or the relationships he has with other characters in Middle - earth.
The characters might have a range of reactions. Some might be intrigued by the creativity of the fanfiction writers. They could see new aspects of their own personalities or the story world explored in ways they hadn't considered. Others might feel a bit violated if the fanfiction changes their motives or actions in a way that doesn't seem true to their original selves. And then there are those who would simply be entertained, especially if the fanfiction adds humor or an exciting new plot twist to their 'Martian' experience.