His character could also develop in terms of his understanding of different kinds of magic. He starts off knowing only about the magic related to dragons. But in the fanfiction, as he watches and interacts with the Guardians, he begins to understand their magic. This could lead to him becoming more open - minded and adaptable. He might start to think about how the different magics could work together to protect both his world and the world of the Guardians. And this new knowledge could also change how he approaches problems back in Berk. For instance, he could try to incorporate some of the Guardians' ideas or magic - like things into his dragon - training methods.
His relationships with others can also be a big part of his character development. If he meets other captives or his kidnappers, how he interacts with them, whether he tries to understand their motives or just fights back blindly, can show his growth. Maybe he starts off being angry and vengeful but then realizes that there's more to the situation and becomes more empathetic.
Since we don't know the specific 'hiccup girl story', it's impossible to say for sure who the main character is. But it's likely to be the girl who has the hiccups.
Toothless' loyalty plays a big part. His loyalty to Hiccup makes him determined to save Hiccup no matter what. This loyalty has developed over time through their shared adventures and experiences.
Her character development would likely be different because of her gender. She might face more discrimination from the Viking community at first. However, her time with the dragons could make her more resilient and determined to prove herself. For example, she may be more cautious in some ways as females in Viking society were often expected to be, but her dragon - raised side could make her bold when it matters.
For Hiccup, start with her insecurities. Maybe she doubts her leadership skills as a female in a male - dominated dragon - riding world. Then, as she interacts with Ruffnut, she could gain more confidence. For example, Ruffnut might encourage her to be more assertive in a certain situation, like when dealing with a difficult dragon. And for Ruffnut, her development could be about becoming more empathetic. She could learn from Hiccup how to think about others' feelings.
It could be Sam Winchester. He's known for his intelligence and his ability to research. If there's a time hiccup, he would be the one trying to figure out the cause and how to fix it using his knowledge of the occult and various historical events.
Well, Hiccup is very resourceful. He could use the environment around him to his advantage. If he is locked in a place, he might find a weak spot in the structure, like a loose board or a hole in the wall. And he could call for Toothless secretly. Toothless, being highly intelligent, could find Hiccup and rescue him. Also, Hiccup could befriend some of Viggo's minions and convince them to help him escape.
Toothless is the most likely one. Their bond is so strong that Toothless would sense Hiccup's distress and come to his rescue. He could fly into Drago's hideout and cause chaos to free Hiccup.
To develop the female Hiccup character, start with her appearance. She could have long, unruly hair that she constantly tries to keep out of her face while working on her dragon - related inventions. Give her a determined look in her eyes. For her personality, she should be brave but also a bit clumsy at times, just like the original Hiccup. She could have a sarcastic sense of humor which she uses to deal with difficult situations.