The main characters are Danny, who is the half - ghost. He has the ability to transform between his human and ghost forms and uses his powers to protect the town from various ghostly threats. Paulina is also a main character. She is often portrayed as a popular and sometimes vain girl at school who then gets involved in Danny's ghostly adventures in different ways in the fanfiction.
One interesting story could be about Paulina realizing Danny's half - ghost nature in a very unexpected way, like during a school play when his powers accidentally go haywire. Another might involve Paulina getting some of Danny's ghost powers transferred to her temporarily and having to deal with the newfound abilities.
Well, one possible plot could be that Sam gets exposed to some ectoplasmic experiment gone wrong. Maybe she was trying to help Danny with something related to the Ghost Zone and ended up getting infused with ectoplasm. As a half - ghost, she'd have to learn to control her new powers, just like Danny did. She might struggle with the idea of being part - ghost at first, especially if it affects her relationships with her friends and family who might be a bit freaked out.
In a sense, it could be thought of as related to the idea of Ghost Rider fanfiction. Danny Phantom is about a boy who becomes a half - ghost and has to navigate a world of ghosts and other strange phenomena. This is somewhat similar to Ghost Rider's journey with his otherworldly powers. But Danny Phantom is an independent creation with its own lore. It has its own backstory for Danny's transformation, his relationships with other characters like his friends and family, and different antagonists. So while there may be some fanfiction - like connections, it stands on its own as a unique story.
It could be Vlad Masters. Since he's always been interested in Danny's half - ghost state, he might see Sam becoming a half - ghost as an opportunity to gain more power or to use her against Danny. He could try to manipulate her new powers for his own evil plans.
A really interesting plotline is when the half - zombie part of Danny starts to influence his ghost side in unexpected ways. Maybe his ghostly powers become more 'undead' like, such as his ice powers now having a decay effect. This can lead to some really cool battles and interactions with other characters.
One great Danny Phantom Ghost King fanfiction is 'The Reign of the Ghost King'. It delves deep into Danny's new role as the Ghost King, exploring how he balances his human life with his ghostly duties. The character development is really well - done in this fic.
For the crossover, a good plot could be that a new type of ghost appears that is immune to Danny's ghostly powers. The Ghost Hunt team, which has encountered a similar situation before, offers their expertise. They introduce Danny to a special type of ectoplasm - based weapon that can harm this new ghost. Danny then teaches them some of his combat moves as a half - ghost to better fight the ghost.
One idea could be that Danny, as a half - ghost, has to prove himself to the Ghost King. Maybe there's a tournament in the Ghost Zone where Danny enters to show his worth. This could lead to some epic battles and alliances with other ghosts.
The scariest part might be when Danny faces really powerful and malevolent ghosts. Their appearance can be quite terrifying, with dark auras and menacing looks.