Luna could also be a good match. Luna's laid - back and cool personality could contrast well with Lucy's more somber and mysterious vampire self. They could bond over their 'outsider' status in a way, with Luna being the rocker chick and Lucy being a vampire. Maybe they could form a band where Lucy uses her vampire - like charm to draw in the crowds.
Clyde might be an interesting choice too. He's Lincoln's best friend and is always getting into various situations. His scientific curiosity could be piqued by Lucy's vampire nature. He might try to find ways to help Lucy control her vampire instincts or even study her in a non - invasive way, leading to some comical and heartwarming moments between them.
Lincoln and Naruto would be a great pair. They both have leadership qualities and a sense of responsibility. Lincoln as the only boy in a large family often has to take charge in certain situations, and Naruto is the leader of his ninja team. They could learn from each other's experiences.
It could be a vampire hunter. He might move to Royal Woods and start suspecting that there is a vampire in the area, which of course is Lucy. He could be very determined and use all kinds of tricks to try and catch her.
I think Lori could be paired well with Lincoln. Since she's the eldest sister, she could be mentoring Lincoln in something, like how to deal with high school or relationships. And then there's Stella. If paired with Lincoln, they could have a story about exploring a new part of town and finding some kind of hidden treasure or secret place that only they know about.
In the case of Lucy, Erza could be a good addition. Erza's strong leadership and combat skills could blend well with Lucy's strategic thinking. As for Hibiki, Genis would be an exciting partner. Genis' intelligence and Hibiki's physical abilities could create a great dynamic in the fanfiction.
Maybe Lucy could find a way to use her vampire abilities to help her siblings in a time of need. For example, when they are facing a mysterious threat in the neighborhood, her vampire powers like super strength or the ability to turn into a bat could come in handy.
Another interesting pairing could be Jeremy and Caroline. Caroline is already a vampire, so she could mentor Jeremy in a way. They could have a fun, flirty relationship where they go on adventures together and learn more about the vampire world as a team. It would be interesting to see how their personalities clash and mesh at the same time.
A third plot idea is that a group of vampire hunters come to Royal Woods believing there is a vampire in the Loud House. Lucy has to use her wits and any vampire friends she might have made to outsmart the hunters and protect her family. This could involve some really exciting chase scenes and moments of clever deception.
I think Spongebob and Lincoln would be really interesting. Spongebob's wacky optimism and Lincoln's attempts to navigate his crazy family life could create some really fun and comical situations. They could learn from each other - Spongebob about family unity from Lincoln, and Lincoln about pure joy and simple living from Spongebob.
One possible fanfiction could be where Lori, as a vampire, struggles to keep her identity a secret within the Loud House. She might have to deal with her newfound cravings for blood while trying not to alarm her family. Maybe she forms an unexpected alliance with one of her siblings who discovers her secret and helps her find alternative ways to satisfy her thirst without harming anyone.
The vampire sisters' characters could develop in terms of their powers as well. At first, they might be afraid to use their powers in front of the Louds, but as time goes on, they might use them more openly for good. For instance, if there's a power outage, one of the sisters could use her ability to see in the dark to help the family find candles. And through these experiences, they become more confident and well - rounded characters within the fanfiction.