Perhaps in this fanfic, Astrid is the one with the mysterious past involving dragons. She has to hide her knowledge and connection to them from the rest of the village. Hiccup, being the popular and more 'normal' Viking, starts to suspect something about Astrid and eventually uncovers her secret, leading to a change in their relationship and the village's view of dragons.
First, you should re - imagine their personalities. Astrid is usually tough and no - nonsense, so as the main character in the reversed roles, she would be more in control of the dragon - related adventures. Hiccup was often underestimated in the original, so in the reversed version, he could be the one who is initially dismissive of Astrid's ideas.
One possibility could be that Hiccup and Astrid find themselves in the Pokemon world. Maybe they start as trainers, with Hiccup having an affinity for Dragon - type Pokemon due to his experience with Toothless. Astrid might be drawn to strong and fierce Pokemon like Arcanine. They could go on adventures together, facing challenges from Team Rocket - like villains in the Pokemon universe.
One idea could be 'Astrid the Braveheart' as it shows her fearless nature. Another could be 'Astrid, the Dragon - friend' since she has a connection with dragons through Hiccup. Also, 'Astrid, the Shieldmaiden' would be great as it emphasizes her warrior side.
A popular one is 'Hiccup and Astrid's Secret Mission'. In this story, they are sent on a top - secret mission to rescue a group of captured dragons. The way they work together, with Hiccup's strategic thinking and Astrid's combat skills, makes for an exciting read.
A more light - hearted plot could be set in a modern - day AU (alternate universe) where Astrid and Hiccup are in high school. Astrid has had a crush on Hiccup for a long time, and the fanfic could detail their journey from being friends to finally admitting their love, with all the typical high - school - related obstacles like popularity differences and peer pressure.
She might be obsessed because she's a big fan of the original story and the fanfics allow her to explore more of Hiccup's story.
Well, on the island in the fanfic, they might have had an adventure involving solving a mystery or encountering a friendly tribe.
She might be initially shocked. In many fanfics, Astrid is a strong - willed character. So, she could take a moment to process Hiccup's confession. Then, she might feel a rush of happiness and finally reciprocate his feelings.
One possible plot could be that Sasuke, in the reversed role, is now the one trying to gain the village's recognition. He might be the underdog with a big dream, like Naruto originally was. He could be using his Sharingan in new ways to protect the village and its people, while Naruto, in Sasuke's role, has a more brooding and solitary nature, perhaps having left the village due to some past event and Sasuke is now on a journey to bring him back.
One great Astrid Hiccup fanfic could be 'Astrid's Discovery'. In this fanfic, Astrid might find a hidden talent of Hiccup that no one else knew about. It could explore their relationship in a new light, with Astrid seeing Hiccup in a whole different way, leading to some really cute and heartwarming moments between them.