One interesting plotline could be that as they turn into dragons, they have to quickly learn how to fly and hunt like real dragons. They might face challenges from other dragons who see them as outsiders in their new dragon forms.
Perhaps a plotline where they turn into dragons and discover a hidden part of the dragon world that was previously unknown to humans. In this new world, they have to find a way to change back while also dealing with the unique dragon politics and power struggles.
Their relationship might become more equal in some ways. As dragons, they are both facing a new and strange existence, so they have to rely on each other more. They might develop a new understanding of each other's strengths and weaknesses.
Another plot could be that Hiccup and Astrid are both on the school's sports team. They are always competing with each other for the top spot. However, during an important competition, one of them gets injured. The other one shows great care and concern, which makes them see each other in a new light and leads to the development of their romantic relationship.
One possible plotline could be Hiccup's journey to earn the respect of the dragons and prove herself worthy of being their queen. Maybe she has to face challenges like rival dragon riders or ancient dragon prophecies.
Perhaps a plotline where Hiccup's refusal causes him to be ostracized from the tribe for a while. During this time, he ventures out on his own and encounters a group of dragons that are also outcasts in their own way. Together, they form an unlikely alliance. As they work together, Hiccup learns more about the dragons' intelligence and emotions. This experience strengthens his resolve to change his tribe's perspective on dragons when he eventually returns. He may have to face challenges like convincing the tribe that the dragons are not a threat and that they can all benefit from a peaceful coexistence.
Another plotline might involve the twins' struggle to fit into human society. After being raised by dragons, they would have different values and behaviors compared to normal humans. This could cause conflict when they try to interact with their own kind. They might face prejudice from those who don't understand their dragon - influenced ways, but also find a few who are intrigued and want to learn from them.
Maybe Astrid is hurt while on a mission to explore a new area. Hiccup, being the caring friend he is, sets aside his own tasks to stay by her side. He could search for a rare herb to heal her wounds. As he does this, their relationship deepens as Astrid realizes how much Hiccup truly cares for her.
One great fanfiction is 'A New Adventure for Hiccup and Astrid'. It shows them exploring a new, uncharted island filled with strange dragons. The story really captures their adventurous spirits as they face challenges together and grow closer in the process.
The world of DreamWorks Dragons is so rich and full of possibilities. In fanfiction, writers can take Hiccup and Astrid on new adventures that we might not see in the original series. For example, they can be in different time periods or face new kinds of dragons. It gives fans the chance to be creative and expand on the story they love. Also, their relationship has so many layers, from friendship to love, and fanfiction can explore all of those aspects in great detail.
There could be a fanfiction where Hiccup and Astrid's kiss is a part of a bet. Astrid bets that Hiccup can't tame a particularly stubborn dragon in a week. If he does, she'll kiss him. Hiccup manages to tame the dragon, and the kiss that follows is a mix of pride, surprise, and the start of a new level of their relationship.
Another plot might involve them trying to start a family. Hiccup and Astrid could face difficulties in having a child, perhaps due to some dragon - related issues or simply the challenges of their own insecurities. They would then have to support each other through this tough time.