One idea could be a crossover with Harry Potter. Yennefer could be a visiting sorceress from another dimension. She might interact with the Hogwarts professors, sharing her knowledge of different magical techniques. Another idea is a crossover with Lord of the Rings. Yennefer could journey to Middle - earth and use her magic to aid in the fight against Sauron. Maybe she'd form an unlikely alliance with Gandalf.
A Yennefer crossover fanfic with the Witcher and Doctor Who could be fascinating. Yennefer could find herself in the TARDIS and travel through time and space with the Doctor. They could encounter various threats and Yennefer's magic would be a unique asset. Or a crossover with Game of Thrones. Yennefer could arrive in Westeros and get involved in the power struggles, using her magic to manipulate the political situation.
You could do a crossover within different fable universes. For instance, take the moral - driven characters from Aesop's fables and put them in the world of Native American fables. The animals in Aesop's fables might learn new values from the Native American fable characters. Also, consider mixing fables from different cultures, like Asian fables and European fables, in a fanfic.
Maybe a crossover with a fantasy world where the Darkness entities interact with magical creatures. For example, they could form alliances or rivalries with elves or wizards, which would lead to a whole new set of adventures and conflicts.
A uzumaki crossover fanfic could involve crossing over with 'Bleach'. Picture an Uzumaki character in the Soul Society, their strong chakra being mistaken for reiatsu. They could bring new fighting styles and techniques to the Bleach universe.
One idea could be a crossover with 'Naruto'. Gon could meet Naruto and they could have a friendly competition in terms of strength and speed. Another idea is a crossover with 'One Piece', where the Hunters from 'HxH' join the Straw Hat Pirates on an adventure. Maybe they could be searching for a rare treasure that has both the allure of the Grand Line and the mystery of the 'HxH' world.
One idea could be a Dalek crossover with the Doctor Who companions. Imagine the Daleks facing off against a group of companions who have to use their unique skills and knowledge to outwit the Daleks. Another could be a crossover with a science - fiction adventure like Star Trek. The Daleks' aggressive nature would contrast greatly with the more diplomatic Starfleet.
One idea could be a crossover with 'Friends'. Jerry could visit Central Perk and have a stand - up comedy session there. His unique sense of humor might either amuse or confuse the 'Friends' gang.
One idea could be a crossover with another popular RPG like Persona. The characters from Twewy could enter the Metaverse in Persona and interact with the Phantom Thieves. They could learn about the different ways of fighting Shadows compared to the Noise in Twewy.
Another interesting crossover could be with a music - themed anime like K - ON!. The Symphogear characters, who are also into music, could have a jam session with the K - ON! girls. And then, unexpectedly, they have to use their combined musical and combat powers to fend off an enemy that is attracted to the powerful music they create.
One interesting idea could be an Overwatch crossover with the world of Harry Potter. For example, Tracer could be a student at Hogwarts, using her time - traveling abilities in magical ways within the school. Another idea is a crossover with the Star Wars universe. Maybe Reinhardt as a Jedi, with his rocket hammer being a unique lightsaber - like weapon. And a crossover with the Lord of the Rings, where Orisa could be a guardian of a certain part of Middle - earth, protecting it from the forces of evil with her shield and gun.
Another idea is a crossover with 'Avatar: The Last Airbender'. The Trollhunters could meet Aang and his friends. They could combine their powers to defeat a common enemy that has the ability to disrupt both the balance of the four elements and the Troll world's magic. For example, they could fight a dark spirit that is draining the magic from the Troll world and using it to spread chaos in the Avatar world.