Another option is a crossover with 'The Little Mermaid'. The characters from the descendants could meet Ariel and her friends underwater. Evie might be interested in the mermaid fashion and could design new outfits inspired by the underwater world.
You should also plan out the plot. Decide on a central conflict. It could be something like a common enemy that both sets of characters have to face. Maybe in a crossover with 'Zootopia', there's a villain who wants to disrupt both the human - like world of the descendants and the animal - centered Zootopia. Then, start writing an engaging introduction that hooks the reader right away.
One interesting idea could be a crossover with "Moana". Elsa's ice powers and Moana's connection to the ocean could create a really cool dynamic. Maybe Elsa accidentally freezes part of Moana's ocean and they have to work together to fix it. Another could be with "Tangled". Rapunzel's long hair and her adventurous spirit combined with Elsa and Anna's journey in Frozen 2 would be exciting. Rapunzel could use her hair to help them climb mountains or cross chasms. A third idea is a crossover with "Beauty and the Beast". Belle's love for books and knowledge could help Elsa understand more about her powers and the history of magic in the Frozen world.
A Thundercats and Star Wars crossover fanfiction would be really cool. The Thundercats could be in the Star Wars universe, and their unique powers and weapons could be a great addition. Maybe the Thundercats could help the Jedi or the Rebels in their fight against the Sith or the Empire. For instance, Cheetara's speed could be useful in battles, and Tygra's illusions could be used to deceive the enemy.
A Digimon and Sailor Moon crossover is an interesting concept. The Digimon could help the Sailor Scouts in their battles against the Dark Kingdom. The magical powers of the Sailor Scouts combined with the digital powers of the Digimon would create a really unique and exciting story. And a Digimon and Avatar: The Last Airbender crossover. The Digimon could be part of the different nations, and they could use their abilities to help Aang and his friends in their quest to restore balance.
One idea could be an Atreus crossover with the world of Harry Potter. Atreus could be a new student at Hogwarts, bringing his own unique skills and knowledge from his Norse mythology background. He might struggle to adapt to the magic of the wizarding world while also showing off his own combat and survival abilities.
Another option is a crossover with a post - apocalyptic world. The garou's survival instincts and combat abilities would be well - suited for this harsh environment. It could either be a lone wolf trying to survive or join a group of survivors, bringing its own set of skills and challenges to the group.
One idea could be a crossover with the Dragon Ball Z and the Naruto universe. Raditz could land in the Hidden Leaf Village and cause chaos, leading to battles with powerful ninjas like Naruto and Sasuke. Another idea is a crossover with the One Piece world. He might end up on the Grand Line and get involved in the Straw Hat Pirates' adventures. Maybe he would try to steal their Devil Fruits or be forced to team up with them against a common enemy.
Perhaps a Gogeta crossover with the DC universe. Imagine Gogeta facing off against Superman. They are both extremely powerful in their own ways. It could explore a battle of strength, speed, and different types of energy. Maybe Gogeta would be intrigued by Kryptonite and how it affects Superman.
One idea could be an Inuyasha and Naruto crossover. Picture Inuyasha in the Hidden Leaf Village, his sword skills and demon powers causing quite a stir among the ninja. Another could be a crossover with Harry Potter. Inuyasha at Hogwarts, trying to figure out magic while also dealing with his own demon - slaying business. Maybe he'd have some interesting interactions with the magical creatures there.
One idea could be a crossover between PVZ and a fantasy world like Middle - earth. The plants could be magical plants with special powers to fight against the zombies which are now some sort of dark creatures from Mordor. For example, the Peashooter could be a small elf - like being that shoots magic peas.