Maybe in this fanfiction, the world of Danny Phantom is being invaded by demons. The exorcist arrives in Amity Park to help. Danny initially doubts the exorcist's methods but soon realizes they can be a powerful ally. They learn from each other's techniques, like Danny teaching the exorcist about ectoplasm and the exorcist showing Danny ancient exorcism spells.
In a more complex scenario, Danny Phantom accidentally crosses into the 'The Exorcist' universe. There, he is mistaken for a malevolent spirit. The exorcist is about to perform an exorcism on him when they start to communicate. Danny has to prove that he is not evil and that his powers can be used to fight the real demons that are plaguing the area. Together, they form an unlikely partnership to cleanse the area of all the supernatural threats.
One idea could be that Danny, with his ghost powers, ends up in the RWBY universe. He could team up with Team RWBY to fight off Grimm that are being influenced by some sort of ghostly energy. His intangibility and flight would be really useful in battles.
One idea could be that Danny's ghost powers somehow interact with the Cybertronian technology in the Transformers Prime universe. Maybe his ectoplasmic energy can power up or disrupt certain Cybertronian devices. For example, he could accidentally short - circuit a Decepticon weapon while trying to use his powers to protect a human from an attack.
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 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.
Another idea is a story about Danny and Star accidentally swapping powers. Danny has to deal with Star's magic while Star tries to control Danny's ghost abilities. It could be a comical yet challenging situation for both of them as they learn to adapt.
One idea could be a crossover where the characters from Danny Phantom and LoliRock team up to fight a common supernatural threat. Maybe the ghosts from Danny's world are being influenced by a dark magic from the LoliRock universe, and they have to combine their powers to stop it.
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.
Well, consider the personalities of the characters. Danny is a young, brave, and sometimes impulsive hero. The exorcist is likely to be more serious and traditional in their approach. In fanfiction, Danny might crack jokes or be a bit more laid - back compared to the exorcist. This could create some interesting dynamics, like the exorcist being frustrated with Danny's non -chalant attitude at times, but also coming to respect his abilities.