First, think about the setting. You could start with them in their normal world, like in the movie, and then introduce a new situation that sets the stage for their love story to develop further.
Begin by describing their characters in more detail than in the movie. What are their hidden desires and fears? For example, Lavagirl might be afraid of losing her powers and Sharkboy could comfort her, which would be a great start to a love - centered plot. Also, you can start with a dialogue between them that shows their relationship dynamic right away.
First, think about the characters' personalities. Sharkboy is brave and connected to the ocean, while Lavagirl is strong - willed and has her fiery nature. Start with a simple scenario, like them meeting in an unexpected place.
Perhaps they could go on a journey to a new magical world where they discover new aspects of their relationship. In this world, they might have to prove their love in different ways, like solving puzzles together.
A believable OC for Sharkboy and Lavagirl fanfiction can be created by carefully considering various aspects. Begin with their origin. Were they born with their powers, or did they acquire them through some event? This origin story can be a great way to add depth. Next, their abilities should have limitations. No one is all - powerful in this world. If they have a power related to the wind, for instance, maybe it only works in certain weather conditions. Their emotions also play a role. If they are scared of heights, this can create interesting situations when they have to fly with Sharkboy. By taking all these factors into account, you can create an OC that feels like it belongs in the Sharkboy and Lavagirl universe.
One common theme could be the power of their love overcoming challenges. Since they both have unique powers, there might be stories where their love helps them face external threats.
Another idea is a story where Sharkboy and Lavagirl go on a journey to discover the origin of their powers. They might encounter some ancient guardians or face challenges that test their friendship and make them grow stronger as they learn more about themselves and their abilities.
I'm not sure about specific "sharkboy and lavagirl love fanfiction" but you can try searching on fanfiction websites like Archive of Our Own or FanFiction.net. There might be some interesting stories created by fans there.
One plot twist could be that Sharkboy turns out to be from a future where Lavagirl has become an evil dictator. He travels back in time to stop her from turning bad. This completely flips their relationship dynamic and adds a whole new layer of complexity to the story.
The kiss in the fanfiction also serves as a plot - driving element. It can change the course of their story. For example, it could be the turning point where they decide to face their enemies together more united than ever, or it could be a moment of realization for their true feelings that then leads to further character development.
Their adventures would likely become more cautious. Instead of just rushing into danger, they would have to think about the safety of the unborn child. So, their battles might be less impulsive.
A cool Sharkboy and Lavagirl fanfiction could be that they swap powers for a day. It would be really interesting to see Sharkboy trying to control lava and Lavagirl swimming around as a shark. Or perhaps a story where they meet other kids with similar but different elemental powers and they all form a team to protect a magical place that is both underwater and volcanic. Also, a fanfic where they get lost in a strange dimension and have to use their combined wits and powers to find their way back home.