Another idea could be that a new and unknown force in their land has the ability to make the impossible happen, like male pregnancy. Hiccup becomes a target for this force for some reason, and Toothless has to protect him not only from the physical threats but also from the social stigma that might come with such an unusual situation. As they face these challenges, their bond deepens and they discover new aspects of their love for each other.
I'm not really into this specific concept, but in general, fanfiction often explores unique relationships. In this case, it might involve a very different take on the characters' bond, perhaps with Toothless in a more human - like form. However, it's a very niche and often not a canon - compliant idea.
Well, it's unique because it combines two very different elements. The relationship between Toothless and Hiccup is already special in the original How to Train Your Dragon story. Adding mpreg to it takes it to a whole new level of creativity. It allows writers to explore uncharted territory in terms of their relationship and how it could develop in such an extraordinary situation.
Well, one possible plot could be that Toothless, in his human form, meets Hiccup's female counterpart. They might start off as strangers but then bond over their love for adventure. Maybe they discover a new, uncharted island together filled with strange and wonderful creatures. Their relationship could grow as they face various challenges on this island, like dealing with a territorial dragon or finding a way to cross a dangerous terrain.
A possible plot could revolve around the female Toothless being injured. Hiccup has to take care of her, and during this time, their relationship deepens. They start to communicate in new ways, and Hiccup learns more about the female Toothless' unique abilities. Or perhaps there is a magical element involved, like a spell that has been cast on the female Toothless, and Hiccup has to break it. This could lead to a journey filled with mystery and self - discovery for both of them.
One plot idea could be Fem Hiccup being the only one who can truly understand Toothless's unique abilities and they go on a journey to discover a hidden dragon world that only Toothless can sense. Another could be Fem Hiccup having to protect Toothless from a group of dragon hunters who are after his special powers.
There are some out there. You can try searching on fanfiction platforms like Archive of Our Own. However, keep in mind that mpreg (male pregnancy) is a very specific and often fictional concept within fanfiction, and the quality can vary greatly.
One possible plot could be that Toothless is under some sort of spell or mind control. Maybe a new villain in the How to Train Your Dragon universe has the power to manipulate dragons. Toothless, being a powerful Night Fury, is forced to kidnap Hiccup. Hiccup, of course, tries to figure out why Toothless is acting this way and how to break the spell.
A 'human toothless x hiccup fanfiction' might tell a story of an alternate universe where Hiccup and Toothless are in a world full of magic. Human Toothless has a special power that only Hiccup can help him control. Their friendship turns into a strong partnership as they face the challenges of this magical realm together.
One common theme is adventure. Since they are based on the How to Train Your Dragon world, they often go on quests together.
One plot idea could be Fem Hiccup discovers a new ability in Toothless that no one else knew about. For example, Toothless can communicate with a long - lost species of dragons. Another could be Fem Hiccup gets lost in a strange land and Toothless has to use his instincts to guide her back home. And also, a plot where Fem Hiccup and Toothless encounter a powerful enemy dragon and they have to work together to defeat it using their unique bond.