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 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.
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.
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.
A frequent theme is secrecy. Danny has to keep his identity as a half - ghost a secret from Valerie for a long time, and this secrecy adds a lot of tension to their relationship. Also, the theme of redemption can be seen in some fan fictions. Valerie may have made some mistakes in the past, like wrongly targeting Danny as an enemy, and she has to find a way to make up for it. Additionally, friendship and loyalty are important themes as they both have friends who support or complicate their relationship.
Since 'lemon' fanfiction is not suitable, I can't recommend any. But if you want to read some interesting Danny Phantom and Valerie Gray fanfiction, look for ones that focus on their relationship development, like how they might overcome their differences and work together. There are likely stories that explore their dynamic in a positive and appropriate way.
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.
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.
One idea could be that Danny gets an illness that affects his ghost powers. For example, he might start losing control over his intangibility or invisibility. This could lead to some really comical or dangerous situations. Another idea is that his friends try to find a cure for his strange ghost - related illness while also keeping it a secret from the town.
There is a fan fiction called 'The Haunting of Valerie Gray'. It starts with Valerie having strange dreams about Danny, which leads her to investigate further. As she digs deeper, she discovers secrets about Danny and herself. It's a really engaging read. Another notable one is 'Valerie's Redemption'. This story focuses on Valerie's journey to redeem herself after some mistakes she made in the past, and Danny plays an important part in that journey.
One idea could be exploring Danny's relationships in a different way. For example, how his friendship with Sam and Tucker might develop if they faced a new supernatural threat. Another could be a story where Danny discovers a new power and has to learn to control it while dealing with school and his ghost - fighting duties. And perhaps a fanfiction where Danny travels to an alternate dimension within the Danny Phantom universe.