In this fanfiction, Nathan could be a new student in town who has a strange connection to the Ghost Zone. Valerie initially suspects him of being a ghost or working with them. But as she investigates, she realizes that he is actually trying to close a dangerous portal to the Ghost Zone that was accidentally opened by one of his experiments. Valerie then decides to help him, and during the process, they face many challenges and dangerous ghosts. Through this adventure, they form a deep bond and become an important part of each other's lives in the Danny Phantom universe.
In a Danny Phantom fanfiction involving Valerie and Nathan, they could become allies in the fight against ghosts. Maybe Nathan discovers Valerie's secret identity and offers his technological expertise to help her upgrade her ghost - hunting gear. This would make them a formidable team, taking on powerful ghosts that Danny might have trouble with on his own.
One idea could be a story where Danny and Valerie have to team up to fight a new, powerful ghost that neither can defeat alone. They start off distrusting each other but as they face challenges, they learn to work together and gradually develop feelings for each other.
One interesting storyline could be Valerie discovers Danny's secret identity in a really unexpected way, like during a ghost attack where she's about to capture him but then realizes who he really is. It adds a whole new layer of drama to their relationship.
Danny is often very well - written. Writers can explore his dual identity further, like how he struggles to balance his normal life and his ghost - fighting duties. In fanfiction, we might see more of his internal thoughts when dealing with Valerie, especially when he's trying to keep his secret from her.
One plot idea could be that Danny and Valerie have to team up to stop a new, powerful ghost that is causing chaos in the town. They start off distrusting each other but as they face challenges together, they begin to respect and understand one another better.
One idea could be that Dash gets in trouble and Danny Phantom, instead of using his powers to embarrass him like he usually might, decides to help him secretly. This could lead to an unlikely friendship between them as Dash starts to suspect that there's something different about Danny but can't quite put his finger on it.
One idea could be that Danny and Jinx accidentally cross paths in a dimension where the laws of magic and the supernatural are all jumbled. Danny is trying to find his way back home and Jinx, initially seeing him as a threat, later realizes they can help each other. They team up to navigate through this strange dimension and along the way, they learn about each other's powers and develop an unlikely friendship.
One idea could be that Danny and Sam have kids in the future and their kids inherit Danny's ghost powers. The story could focus on how they learn to control their powers while also dealing with normal kid stuff like school and making friends. It would be interesting to see how Sam, as a mom, guides them through this.
One interesting plot could be Valerie finding out about Danny's ghost powers in a very public and dangerous situation. Maybe they are in the middle of a fight with a powerful ghost and Danny has no choice but to reveal himself to save Valerie. Another plot could be Valerie slowly suspecting Danny over time as she notices little things about his behavior that seem strange in relation to the ghost attacks. For example, he always seems to disappear right before a ghost shows up.
You can try Archive of Our Own (AO3). It has a large collection of fanfictions for various fandoms, including Danny Phantom. Just use the search function and type in 'Danny Phantom and Valerie Gray' to find relevant stories.