Dumbledore could be an interesting character to focus on in this crossover. He is so wise and experienced in the magical world. When Johnny Test arrives in Hogwarts, Dumbledore would be the one to guide him, while also being intrigued by Johnny's different way of thinking. Dumbledore could see potential in Johnny that others might not, and their interactions could lead to some really interesting plot developments, like Dumbledore using Johnny's ideas to come up with new magical theories or defenses for Hogwarts.
Doctor Strange would be an interesting character to focus on in a Harry Potter MCU fanfiction. He already has knowledge of magic in the MCU, but it's a different kind of magic compared to that in Harry Potter. He could compare and contrast the two magics, and perhaps even learn new spells from the Harry Potter universe. His presence could also bridge the gap between the two universes in terms of magic.
Hermione Granger would also be an interesting character to focus on. She's extremely intelligent and curious. In a crossover, she would be the one trying to figure out how The Flash's powers work from a scientific and magical perspective. She might even try to find a way to combine magic and the Flash's speed for some greater good. Her inquisitive nature would make for some great interactions with The Flash and would add a lot of depth to the crossover story.
I think it would be really interesting to focus on Hermione. She's so intelligent and curious. In Middle - earth, she could study the different magic and lore there. She might be the one to figure out how to combine the magic of the two worlds. For example, she could try to find a way to use the magic of Middle - earth to defeat Voldemort or help the Fellowship in a different way.
Harry Potter himself could be a great focus. Imagine him being introduced to the Halliwell sisters' way of life. His sense of justice and determination would be put to the test in a different magical context, and his relationship with Piper could develop in interesting ways as they learn from each other's magical experiences.
Harry Potter himself would be really interesting. He's used to facing dark wizards and magical threats, but the survival horror aspects of Until Dawn would be a whole new challenge for him. His courage and determination would be put to the test in a different way, like having to make quick decisions in a life - or - death situation without relying solely on his magic.
I think Hermione would be really interesting. She's so intelligent and resourceful in the 'Harry Potter' world. In a fanfiction with 'Legends of Tomorrow', she could use her vast knowledge of magic to help the Legends understand and deal with magical threats they encounter during their time - traveling adventures. She might be able to figure out how to combine magic with their technology in ways no one else could.
Harry Potter himself would be very interesting. Since he has already faced the fully - formed Voldemort in his own time, seeing Tom Riddle in the past and understanding how he became who he is could be a great character arc for Harry. He could be conflicted between his hatred for Voldemort and his pity for the young Tom who still has a chance at redemption.
I think it would be really interesting to focus on Hermione. Her thirst for knowledge would make her eager to learn about the world of Eragon, especially the dragon - riding and the different types of magic. She could also bring her logical thinking and problem - solving skills to the table, which would be very useful in both worlds.
I think Harry Potter himself would be very interesting. Imagine him in Neverland, a place so different from Hogwarts. He could bring his courage and sense of justice from the wizarding world and apply it in the new setting. His magic skills would also be fascinating to see in the context of Neverland, like how he would use spells against the likes of Captain Hook or other threats there.
Definitely Harry Potter himself. His journey through time could be a way for him to gain more understanding of his parents and the events that led to their deaths. He could also try to change some things in the past to make the present better. For example, he could try to prevent Voldemort from ever becoming so powerful in the first place. And seeing Harry interact with the people from the past, like his grandparents or young Dumbledore, would be really fascinating.