In a crossover fanfiction, Rick could be intrigued by the strange anomalies in Gravity Falls. He decides to study them, dragging Morty along. They run into the Pines family, and Rick starts making deals with Grunkle Stan to get access to some of the more mysterious areas of the town. However, his actions start to awaken some long - dormant and dangerous entities in Gravity Falls that both sets of characters have to deal with.
A possible crossover fanfiction could involve Dipper and Mabel trying to get Rick to help them solve some of the really tough mysteries in Gravity Falls. Rick might initially refuse, but then Morty convinces him. And along the way, they get into all sorts of misadventures with Bill Cipher maybe getting involved and trying to use Rick's technology for his own evil purposes.
One possible plot could be that Rick and Morty accidentally portal into the Gravity Falls universe. They meet Dipper and Mabel, and Rick's technology starts malfunctioning because of the strange magical forces in Gravity Falls. Morty and Dipper team up to try and fix it while Mabel tries to get Rick to participate in some of her wacky Gravity Falls activities.
Rick and Dipper would be really interesting. Rick's cynical and scientific view would clash with Dipper's curious and somewhat naive nature. Dipper would be both fascinated and a bit intimidated by Rick's intelligence and his access to other dimensions. Rick might see Dipper as a young, impressionable mind that he could either corrupt or mentor in a strange way.
Definitely Rick and Dipper. Rick is this super intelligent, jaded scientist who has seen so much of the multiverse, and Dipper is this young, eager mystery - solver. Their interactions would be really interesting as Dipper would be constantly asking Rick questions and Rick would be either annoyed or reluctantly impressed by Dipper's inquisitiveness.
Rick and Grunkle Stan would be really interesting. They're both kind of cynical in their own ways. Rick could be dismissive of Stan's 'hustles' at first, but then they might find common ground in their experiences dealing with the strange and unknown. They could end up swapping stories about the weird things they've seen in their respective universes.
A cool Rick and Morty crossover fanfiction idea is with 'Back to the Future'. Marty McFly could end up in Rick's dimension and they could team up to fix some time - space continuum issues that Rick's inventions caused. Or a crossover with 'The Simpsons'. Homer could be awed by Rick's intelligence and Morty could make friends with Bart. Also, a crossover with 'Star Trek' would be amazing. The crew of the Enterprise might be both intrigued and horrified by Rick's unethical scientific experiments.
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.
One idea could be that the characters from Rugrats somehow end up in Gravity Falls. Maybe the babies follow a strange glowing bug that turns out to be a magical creature from Gravity Falls. And Tommy could befriend Dipper, and they start exploring the mysteries of Gravity Falls together. The Rugrats' naivete could add a new comical element to the Gravity Falls mysteries.
One idea could be that Dipper and Mabel from Gravity Falls end up in the SVTFOE universe. They could team up with Star to battle some sort of interdimensional evil that threatens both their worlds. Maybe they discover a connection between the strange creatures in Gravity Falls and the magic in SVTFOE.
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.