Well, it depends on the specific fanfic. Sometimes the characters could be in awe of the visuals and the story. They might also start imagining themselves in that world and having similar adventures. Or they could be critical and compare it to other similar shows.
Well, it depends on the characters' personalities and their prior connection to the How to Train Your Dragon universe. Some might love the fanfiction for its creativity, while others could be critical if it strays too far from the original story.
Astrid would probably be very surprised at first. She might be a bit jealous of Hiccup's new appearance as a girl, but also curious about how this change has affected Hiccup's personality. Stoick would be shocked and might be a bit overprotective. He'd have to adjust to the idea of his son being in a different form. Snotlout would likely make some inappropriate jokes at first, but then gradually come to accept Hiccup as she is. And Toothless? He might be a bit confused at first, but his bond with Hiccup would likely remain strong regardless of the physical change.
One popular theme is the further adventures of Hiccup and Toothless. Writers often explore new lands and challenges that they might face. For example, they might encounter a new type of dragon with unique abilities.
Some characters might be amused. For example, Hiccup could find it interesting to see different interpretations of his adventures in HTTYD 2. He might laugh at the creative liberties taken in the fanfiction.
Well, when Hiccup is a dragon in fanfiction, it could be because of an ancestral connection or a mysterious experiment. This could open up new storylines and allow for exploration of his identity in a completely different way. Maybe it's a way to show his ultimate empathy and unity with the dragon species.
Hiccup would likely approach it with enthusiasm. Since he loves his dragons and his adventures, he would be eager to see how others imagine the world of 'How to Train Your Dragon'. He might find some fanfictions that give him new perspectives on his own life and relationships. Toothless, being a dragon, might not understand all the words but would react to the emotions in the stories. If the fanfiction shows a happy moment between him and Hiccup, he might get excited and start making his little happy dragon noises. Astrid would probably analyze the fanfiction carefully. She would look for any inaccuracies in how her character is portrayed, especially when it comes to her skills as a dragon rider and her relationship with Hiccup.
Hiccup in the fanfiction typically trains by forming strong bonds with the dragons first. He shows them kindness and respect, and then gradually introduces training exercises that are fun and challenging for both him and the dragons.