In the fanfiction, perhaps there's a moment when Hiccup gets injured while protecting the village. Astrid stays by his side day and night, taking care of him. She reads to him, makes him his favorite food, and in those quiet days, they realize how much they mean to each other. Their love deepens as they share these tender moments.
It develops gradually. At first, they might be just friends who respect each other's skills. But as they go on more adventures together, they start to notice little things about each other. For example, Hiccup notices how Astrid is always the first to volunteer for dangerous tasks because of her bravery. And Astrid sees how Hiccup's intelligence always gets them out of tough situations.
I'm not sure if there is an official such fanfic. Fanfics can cover a wide range of themes and scenarios, but this one might be a bit controversial or not in line with the original story's tone in some views. However, the fanfic community is so vast that there could potentially be something like it out there.
No, writing such sexually explicit fanfic is not appropriate as it involves inappropriate and vulgar content that goes against moral and ethical standards.
One common theme is adventure. Since they live in a world full of dragons, many fanfics will have them going on quests or exploring new lands. Another theme is friendship. Their bond is a strong part of the story.
One common theme is adventure. Since they are dragon riders, many fanfictions involve them going on quests, exploring new lands, and facing various challenges. For example, they might go on a journey to find a lost dragon or a magical item.
They're popular because they have a great dynamic. Hiccup is the more gentle and inventive type, while Astrid is strong and fierce. This contrast makes for interesting relationship development in fanfictions.