Well, perhaps there could be a fanfiction where Hiccup and Elsa are both summoned by a powerful wizard to help with a prophecy. They don't trust each other at first, but as they face the challenges set by the wizard, which include tasks that require both fire (from Hiccup's dragon) and ice (Elsa's power), they start to respect and care for each other.
One idea could be that Hiccup and Elsa accidentally meet in a magical realm between their two worlds. They discover that their powers of ice (Elsa) and dragon - taming (Hiccup) are somehow related to an ancient prophecy that involves saving both of their kingdoms from a common threat, like a powerful fire - breathing monster that is immune to normal attacks but can be weakened by the combination of ice and the special bond Hiccup has with his dragon.
One plot idea could be a story where Hiccup, Heather and Lemon are on a quest to find a rare dragon. Along the way, they face various challenges that test their friendship and skills. Hiccup's dragon training knowledge, Heather's combat skills, and Lemon's unique problem - solving abilities all come into play as they battle the elements and other dragon - trainers who want the dragon for themselves.
One idea could be a story where Hiccup and Tuffnut are on a wild adventure together and they start to understand each other's perspectives in a new way. Maybe they get lost in an uncharted land and have to rely on each other's skills to survive. Another could be a story where they compete in a friendly but intense dragon - racing tournament, which brings out their rivalry and also deepens their friendship. And a third idea could be that they accidentally discover a hidden treasure that has a magical effect on their relationship, making them see each other in a whole new light.
A plot could involve Elsa's ice powers acting up during her pregnancy. Hiccup, being from a more technological and dragon - friendly world, tries to find ways to help her control it. They might seek the help of Toothless and other magical creatures in their world. Maybe they face opposition from some of their people who are not happy about their union, especially with a baby on the way. But they stand strong together and prove that love can bridge any gap.
Well, one interesting idea could be their exploration of each other's magical abilities. Hiccup could be fascinated by Elsa's ice powers and they could learn from one another about controlling and using their unique gifts.
One idea could be that Percy, with his water powers, and Elsa, with her ice powers, team up in a magical realm. They could face a common enemy that threatens both their worlds. And as they work together, they start to understand each other's powers more deeply, leading to a strong bond.
Another plot could be that they are both in a high - school sports team. Hiccup is not as athletic as the others, but Astrid helps him train. During the training sessions, they start to bond. There could be a moment when Hiccup gets injured and Astrid takes care of him, which makes their relationship take a new turn.
A possible plot could be that there is a lemon - themed festival in Arendelle. Hans, who has returned after his banishment, tries to win Elsa's forgiveness during this festival. Elsa is initially skeptical but as they both participate in the lemon - inspired games and activities, they start to develop a new relationship that is different from their previous encounter.
A possible plot is that Elsa's kingdom is threatened by a force that is related to the same kind of threats the Avengers face. The Avengers hear about her and her powers and travel to her world to offer their help. Along the way, they learn about her backstory, and she learns about their heroics. Together, they combine their powers to save her kingdom and in the process, Elsa decides to join the Avengers on some of their adventures in their own universe.
One plot idea could be that the reader is a new arrival in Berk. Hiccup takes it upon himself to show the reader around, introducing them to the ways of the Vikings and the dragons. Along the way, they face challenges like a sudden dragon attack, and they have to work together to protect the village. This builds their bond and friendship, which could potentially turn into a romantic relationship over time.