Adventure is a very common theme. Since Toothless is a dragon, he often goes on exciting journeys in different crossover worlds. Another common theme is friendship. For example, when he crosses over to a world like the Avengers, he forms new friendships. Also, discovery is common. He discovers new things about different worlds and cultures in the crossovers.
Empowerment is also a theme. Fem Toothless is usually depicted as a strong and independent character, capable of taking on challenges on her own. And there's also the theme of discovery, whether it's about her own abilities or about new things in the world around her.
One common theme is friendship. Many fanfictions focus on the deep bond that can form between a female character and Toothless. Another theme is adventure. The female character often goes on exciting adventures with Toothless. For example, they might explore new lands or face dangerous enemies together.
One common theme is loyalty. Toothless is known for his loyalty, and in fanfiction, this loyalty often extends to his love interest. For example, he will always protect and be there for the one he loves.
In many pregnant Toothless fanfictions, the theme of adaptation is prominent. Toothless has to adapt to his changing body and new responsibilities. There could be a theme of mystery as well, especially if the pregnancy is something that is not fully understood in the context of the story. And of course, the theme of love and loyalty among his friends and allies as they support Toothless through this unique situation is also quite common.
Friendship is a very common theme. Their unique bond is often explored, like how they support each other in different situations.
One common theme could be the anticipation and excitement around the new arrival. It might explore how the characters in the story prepare for the baby Toothless.
Friendship is a common theme. Since they are both unique creatures from different fictional universes, their coming together and forming a bond is often explored.
Friendship and acceptance are also prevalent themes. Human Toothless has to find friends in the human world who will accept him for who he is, especially considering his unique origin. There are often heart - warming stories of how he forms deep bonds with other humans despite his differences.
One common theme is the growth of the dragon family. Since Toothless breeds, it often explores how the new dragons grow and develop, and how Hiccup adapts to having more dragons around. Another theme is the continuation of the bond between Hiccup and Toothless, even as Toothless becomes a father.
Another theme could be the discovery of new abilities. Maybe they find out that together they can do things that they couldn't do alone, like access a hidden part of their dragon world or unlock a special power. This theme allows for a lot of creativity in the fanfiction writing.