It could be about a post - apocalyptic world where the environment has been so severely damaged that basic survival is a struggle. For example, there might be no clean water or breathable air, and the few remaining humans are constantly fighting over scarce resources.
The challenges they face in this unfit world can shape their values. A character might initially value material possessions but, after seeing how meaningless they are in a world on the verge of collapse, come to value things like human connection and community. This transformation can be a key part of their development.
Another theme could be survival. In such a world, characters would have to struggle to stay alive. They might face shortages of food, water, and shelter, and have to constantly fight off threats from other desperate people or dangerous creatures.
He could fit in as a special guest lecturer. His knowledge of different magics would make his classes very popular. Students would be eager to learn from him, especially about his adventures in Middle - earth.
Deadpool would likely be a very chaotic element in the Naruto world. In a fanfic, he might arrive through a portal that was opened accidentally. His combat style would be completely different from what the ninjas are used to. He doesn't really have a set of jutsu like the ninjas, but his acrobatic fighting and use of guns and swords would be a novelty. He could form an unlikely friendship with Naruto. Naruto would be intrigued by Deadpool's immortality and try to understand it, while Deadpool would be interested in Naruto's chakra and the whole concept of ninjutsu.
Gwendy can fit in as a new friend to the main characters. She could join Harry, Ron and Hermione on their adventures and offer a fresh perspective. Maybe she has a different approach to solving problems, like using her knowledge of Muggle technology in a magical way.
He could be a new type of hero. Maybe he starts as an unknown entity and quickly rises in power and reputation. His unique jutsu like the Sharingan (if he somehow acquired it in the crossover) would make him stand out. He could join forces with the Avengers and teach them new combat techniques based on his ninja skills.
He could be a long - lost relative of one of the characters. For instance, if he's related to Bill, it could create a whole new dynamic. Rav might try to reconcile Bill and the Bride, or he could be caught in the middle of their feud, not really knowing which side to take.