One common theme is the clash of different worlds. Harry comes from a world of magic and wizards, while Stefan is from a world of vampires. So, there's often exploration of how these two very different worlds collide and interact.
One common theme is self - discovery. Stefan often has to figure out his own sexuality and come to terms with it. For example, in many fics, he might start off confused but gradually realize his feelings for other male characters.
The theme of rivalry also pops up a lot. They are often in competition for things like Elena's love or power in the vampire world. But at the same time, there's the theme of unity. In the face of greater threats, they come together and their bond is strengthened. For example, in some fanfics, when a new, more powerful vampire arrives in Mystic Falls, they put aside their differences to fight it.
Another theme is 'redemption'. Stefan has his own dark past, and Bonnie is often portrayed as a powerful and good - hearted character. Fanfics may explore how Stefan can find redemption through his relationship with Bonnie, or how Bonnie helps him overcome his inner demons.
One common theme is love triangle. Since Bonnie, Damon and Stefan are all connected in the Vampire Diaries universe, the love triangle between them is often explored. It creates a lot of drama and tension.
Romance is likely a very common theme. Writers might explore how Harry and Lisa could fall in love, perhaps over coming cultural or world - view differences. They could start off as strangers and gradually develop feelings for each other through shared experiences in a new, made - up world.
Another theme is self - discovery. Harry and Cho are both at an age where they're still figuring out who they are. Fanfics often explore how their relationship helps them in this journey, like Harry becoming more in touch with his emotions through his interactions with Cho.
Another theme is self - discovery. The characters of Harry and Louis are often on a journey of self - discovery in relation to their feelings for each other. In some fanfics, they have to figure out who they are and what they really want in terms of their relationship.
One common theme is the exploration of family bonds. Since James is Harry's father, many fanfics focus on how they could have interacted if James had been alive. Another theme is the passing on of knowledge or skills from father to son.
One common theme is friendship. Since both Luna and Harry are unique characters in the Harry Potter universe, their friendship is often explored in fanfics. Another theme is the discovery of hidden magic. Luna's penchant for the strange and unknown often leads them to find new magical things together.
Rebellion against the status quo can also be a theme. Sirius is a bit of a rebel, and he encourages Harry to question things. So in many fanfics, they might be involved in actions that go against the traditional rules of the wizarding society. And of course, the theme of friendship - a deep, unbreakable friendship that could be seen as more than just friendship in some interpretations.