Another option is FanFiction.net. However, the quality can vary a great deal. Look for stories with high review scores and lots of favorites. Sometimes, you might also find some crossover fanfictions on Tumblr. Some fans post their works there, or they might reblog interesting ones they've found.
You could also check out some dedicated Don't Starve or Gravity Falls fan forums. The fans there are really into the shows/games and might have written or know of some great crossover fanfictions. Just search through the fanfiction sections of those forums.
Well, one idea could be that the characters from Don't Starve end up in Gravity Falls. The strange and magical elements of Gravity Falls would be a huge challenge for the Don't Starve characters who are used to their own, albeit also strange, world. For example, Dipper could try to help Wilson figure out how to get back to his world while they both deal with the mysteries and threats in Gravity Falls.
First, you need to understand the two universes well. Know the characters, their personalities, and the rules of their worlds. For Gravity Falls, know about the mysteries, the strange creatures, and the relationship between the characters. For MLP, understand the magic, the different pony types, and the importance of friendship. Then, come up with an interesting concept for the crossover. It could be a simple visit between the two worlds or a more complex situation like a shared threat that forces them to work together.
You can start by looking on fanfiction platforms like Archive of Our Own (AO3). There are often tags related to 'Gravity Falls', 'Pacifica' and 'Mabel' that can help you narrow down the search. Some writers might also post their works on Tumblr, where you can search for Gravity Falls fanfiction blogs.
One great place to start looking for Hilda and Gravity Falls crossover fanfiction is Archive of Our Own (AO3). There are many talented writers who combine the two universes in interesting ways. For example, some fanfics might have the characters from Hilda exploring the mysteries of Gravity Falls, or vice versa. The crossovers often play on the similarities between the two shows, like their focus on the supernatural and the adventures of young protagonists.
A great one is 'Naruto in Gravity Falls'. It focuses on Naruto being transported to Gravity Falls. He has to adapt to this new world while still having his ninja skills. His presence in Gravity Falls also starts to affect the balance of the town, and he has to work with the local characters to fix things. The fanfic does a good job of blending the two very different settings.
One popular 'creepypasta crossover gravity falls fanfiction' might be those that combine the strange and mysterious elements of Gravity Falls with the eerie nature of Creepypasta. For example, there could be a story where a Gravity Falls character encounters a well - known Creepypasta entity like Slenderman in the woods of Gravity Falls. The unique settings and characters of Gravity Falls offer a great backdrop for Creepypasta - style horror to unfold.
Another common theme is friendship. The main characters in both shows are young and form strong bonds with their friends. In crossover fanfiction, you'll often see the characters from Hilda befriending the characters from Gravity Falls. They might rely on each other's unique skills and knowledge to get through various challenges, like when Hilda uses her wilderness skills and Dipper uses his mystery - solving abilities to face a common threat.
Mystery is also a big theme. Both Naruto and Gravity Falls have elements of mystery in their own right. In the crossovers, these mysteries blend. For instance, the mystery of the Akatsuki's goals in Naruto might get intertwined with the mystery of the Gravity Falls anomalies. And of course, there's the theme of self - discovery. The characters, whether from Naruto or Gravity Falls, learn more about themselves as they interact with the new and different characters from the other universe.
Another idea is a crossover of the Upside Down and the Weirdness of Gravity Falls. Imagine Eleven using her powers in Gravity Falls and discovering new and strange things about the town. The kids might explore areas where the laws of physics seem to be a mix of both their worlds. For example, they could find a portal that leads to a place that has elements of both Hawkins and Gravity Falls.
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.