Yes, there are. Some fanfics might focus on minor characters from the original series and give them more depth. For instance, a fanfic could explore the backstory of Neville Longbottom in great detail.
I'm not sure specifically as it's a fanfiction. But it might combine the world of Harry Potter with the Pokémon Ho - Oh. Maybe it has Harry and his friends encountering the legion of Ho - Oh in some magical adventure.
There's 'Magic and Brotherhood'. It's a fanfic where the themes of family and loyalty from 'Oh Brother' are intertwined with the loyalty and friendship seen in Harry Potter. The characters from 'Oh Brother' end up in the wizarding world during a time of crisis and they use their own brand of street - smartness along with the magic they start to learn to help Harry and his allies. It's a great read for those who like to see different universes collide.
Well, 'oh hell no' is an expression of strong disapproval or refusal. In the context of 'Harry Potter fanfic', it might mean that someone really doesn't like a particular Harry Potter fan - created fictional work. Maybe they find the plot too outlandish, or it goes against their idea of the original Harry Potter universe.
A crossover could also involve the Yu - Gi - Oh GX characters coming to the Hogwarts world. They could be enrolled as special students. Jaden could use his dueling skills to face off against the dark wizards that threaten Hogwarts. He might even combine his dueling spirit with magic spells. Syrus could be in awe of the magical creatures at Hogwarts and try to find a way to incorporate them into his dueling strategies. Chazz would probably be a bit of a troublemaker, challenging the Hogwarts students to duels and causing some chaos in the halls of Hogwarts.
I don't know for sure, but it's likely that Harry Potter himself would be one of the main characters since it has his name in the title. And perhaps his friends like Hermione and Ron could also be involved.
First, you need to be well - versed in both universes. Read all the Harry Potter books and watch 'Oh Brother' if it's a movie or show. Then, come up with an interesting concept like a character crossover. Decide how the characters from 'Oh Brother' will interact with the magical world and its inhabitants. For example, will they be amazed by magic or will they be skeptical at first? Keep the essence of both the Harry Potter world (the magic, the houses, the dark vs light theme) and the 'Oh Brother' world (the family bond, the humor, the sense of adventure).
Someone might say it if the fanfic contains really bad writing. Like if the grammar and spelling are atrocious, it can be a turn - off. Also, if the story is just plain boring or the characters are not well - developed.
I really liked 'Fem Harry's Yu - Gi - Oh Adventure'. In this fanfiction, fem Harry Potter discovers a portal that leads her to the Yu - Gi - Oh universe. It's a fun read as she tries to adapt to the new rules and make friends in that world while still having her Hogwarts - trained magic at her disposal. It has a lot of action and some really cool crossover moments.
In some fanfictions, there might be a scenario where the Millennium Items from Yu - Gi - Oh have some sort of connection to the magical artifacts in Harry Potter. For instance, the Philosopher's Stone could have an unexpected interaction with the Millennium Puzzle. This could lead to all sorts of adventures and challenges for the characters from both universes. The characters would have to figure out how to use the powers of both worlds to overcome the obstacles.