Well, a really cool fanfiction could be about Danny's class getting superpowers from the Ghost Zone and they form a sort of superhero team with Danny. They have to learn how to use their new powers while also dealing with the politics and dangers of the Ghost Zone. There could also be a fanfiction where the Ghost Zone starts to merge with the human world and Danny's class has to help him stop it before it's too late.
There might be a fanfiction where Danny takes his whole class on a 'field trip' to the Ghost Zone for a science project. But things go wrong when a powerful ghost decides to use the students as hostages. In some fanfictions, Danny's classmates discover the truth about his double life in the Ghost Zone in a very unexpected way, like during a school play that somehow opens a portal to the Ghost Zone.
One interesting fanfiction could be where Danny's class accidentally gets transported to the Ghost Zone. They have to rely on Danny's ghost powers to survive and find their way back. Another could be a story where a new student in Danny's class has a secret connection to the Ghost Zone and they team up with Danny to face a new threat from there.
You can try looking on fanfiction.net. There are often some great stories there about Danny's class and the Ghost Zone. One I remember has Danny's class getting trapped in a mini - Ghost Zone inside the school. It was really exciting as they had to figure out how to escape while also dealing with mini - ghosts.
One interesting plot could be Danny facing a new, extremely powerful ghost in the Ghost Zone who challenges his title as the King. This ghost might have unique powers that Danny has to figure out how to overcome.
In a Danny Phantom Ghost Zone Fanfiction, a great plot could be that Danny discovers a portal within the Ghost Zone that leads to an alternate dimension full of even more powerful and strange ghosts. He has to explore this new place to find a way to close the portal before the dangerous ghosts from that dimension invade the regular Ghost Zone and then the human world. Another idea is that there's a competition among ghosts in the Ghost Zone, and Danny gets involved. He has to use his wits and powers to win the competition, which has a great reward that could help him protect both the Ghost Zone and the human world better. Also, Danny could find a ghostly artifact in the Ghost Zone that gives him new powers, but also attracts the attention of all the wrong ghosts, leading to a series of intense battles.
One idea could be that during the field trip, Danny discovers a new type of ghost that has powers he's never seen before. This ghost could be friendly at first but then turn out to have a hidden agenda that endangers the whole class.
There's also 'Phantom's Unlimited Potential'. This fanfiction delves into Danny's untapped powers. It shows how he discovers new ways to use his ghost powers, like being able to manipulate time on a small scale within the Ghost Zone. This gives him an edge over other powerful ghosts he encounters.
One interesting fanfiction could be where Danny and Dani Lemon team up to defeat a new and powerful ghost. In this story, they might discover new powers within themselves as they face the challenges together.
One interesting 'Danny Phantom Danny and Ember' fanfiction could be where Danny and Ember team up to fight a new, powerful ghost that threatens both the human world and the Ghost Zone. They start off as reluctant allies but gradually come to respect each other's powers.
One interesting fanfiction could be where Danny Phantom sings to calm a ghostly entity. In this story, his singing has a special power that can soothe the angry spirit, and it's a new ability that he discovers by accident during a particularly tough ghost - fighting situation.
There might be a fanfiction where the scars on Danny are not just physical but also represent his emotional traumas. Each scar could be linked to a different difficult event in his life as Danny Phantom. Like the first scar he got was when he first faced a major ghost enemy and it serves as a reminder of how far he's come in his journey.
One great fanfiction could be where Danny has to deal with new threats in the Ghost Zone while trying to balance his life as a prince and a human. Maybe he forms an alliance with some unexpected ghosts to protect his throne.