What are some interesting plot ideas for a Danny Phantom and Gravity Falls crossover fanfiction?

One idea could be a crossover where Danny Phantom visits Gravity Falls. He could use his ghost powers to help the Pines family solve some of the mysteries there, like dealing with a supernatural entity that's beyond the normal Gravity Falls weirdness. Maybe he teams up with Dipper to fight a ghostly creature that has been causing trouble in the forest.

One idea could be that the characters from Gravity Falls end up in the FNAF world. Dipper might be intrigued by the mystery of the haunted animatronics and try to solve it using his journal. Mabel could befriend the more friendly - looking animatronics, like Chica, and try to make them cute accessories. Another plot could involve the FNAF villains getting loose in Gravity Falls and the Pines family having to use the town's unique magic to stop them.

One idea could be that Dipper and Mabel end up in the Undertale universe. They might meet Sans and Papyrus. Dipper could be intrigued by the magic system in Undertale and try to study it, while Mabel would probably befriend the friendly monsters right away. Maybe they get involved in the conflict between humans and monsters in the Undertale world and use their Gravity Falls knowledge to find a new solution.

Perhaps there is an ancient evil that threatens both Gravity Falls and Hilda's world. The characters need to combine their unique skills and knowledge. Dipper's knowledge of the strange and supernatural from Gravity Falls, along with Hilda's experience with the magical creatures in her world, would be crucial. They could start by gathering allies from both worlds, like Wendy and David. Then, they embark on a journey to find the source of this evil and a way to stop it. This would involve a lot of exploration, mystery - solving, and character development as they learn from each other.

One idea could be a Gravity Falls and Steven Universe crossover. Dipper and Mabel could meet Steven and the Gems. Maybe they'd team up to solve a mystery that involves both Gravity Falls' strange phenomena and the Gem-related threats. It would be cool to see how the different magical elements interact.

The interactions between Ford Pines and Danny's parents could be fascinating. Ford, with his vast knowledge of the strange and supernatural, might be intrigued by Danny's parents' attempts at ghost hunting, even if their methods are a bit more primitive compared to his own scientific investigations. Meanwhile, Danny's parents might be in awe of Ford's knowledge and the things he has discovered in Gravity Falls. This could lead to some comical moments as well as some interesting exchanges of ideas about the nature of the supernatural.

Maybe Danny gets transported to a different dimension where there is a harem - like society. The local girls there are intrigued by his ghost powers and his heroic nature. They start following him around, and he has to figure out how to deal with their attention while also trying to find a way back home. Some of the girls might be from different species, which could add more interesting elements to the story, like different cultural norms regarding relationships.

One idea could be that Danny's ghost powers start to malfunction in the TMNT's dimension, causing strange ghostly events that the turtles have to help him fix. Another could be a villain from Danny's world teams up with one of the TMNT's foes, forcing the two groups to work together. Maybe Danny accidentally gets sent to the sewers where the turtles live and they initially mistake him for a new type of mutant.

A possible plot is that a powerful ghost in Danny's world has a connection to an ancient demon in Inuyasha's world. This connection is causing chaos in both worlds. Danny and Inuyasha meet and initially are at odds because they don't trust each other. But as they start to learn about the threat they face together, they begin to work together. Danny uses his energy blasts and Inuyasha uses his Tessaiga to fight the combined forces of the ghost - demon entity.

Well, there could be a story where Danny's ghost sense starts acting up in the Naruto world. It turns out that there are some spirits there that are similar to the ghosts in his world. Naruto thinks Danny is crazy at first but then they discover that these spirits are tied to an ancient curse. Together, they have to find a way to break the curse. Danny uses his ability to communicate with ghosts to learn more about the spirits, and Naruto uses his determination and strength to face any physical challenges that come their way.