What are some interesting ideas for a Hellsing Ultimate crossover fanfiction?

You could also focus on an alternate universe where the events of Hellsing Ultimate took a different turn. Maybe Integra made different decisions early on, which led to a completely different power structure within the organization and different battles against the forces of evil.

An interesting OC for Hellsing Ultimate fanfiction could be a young orphan who is taken in by the Hellsing Organization and trained to be a part of their ranks. This OC could have a special connection to one of the main characters, like Alucard. They might start off as a naive and inexperienced recruit but grow into a strong and reliable member of the team, facing various challenges and moral dilemmas along the way.

One idea could be to create a male OC who is a former vampire hunter turned vampire. He could struggle with his new nature while still having a sense of justice from his past. He might secretly help the Hellsing Organization against more dangerous vampires, creating an internal conflict within himself.

One idea could be to have Alucard from Hellsing meet the vampires in Twilight. Maybe Alucard would be amused by their 'tame' nature compared to his own blood - thirsty self. He could show them what a real vampire is capable of in a fight.

Another possibility is a crossover with 'Tokyo Ghoul'. The ghouls' unique abilities and the vampire - hunter theme of 'Hellsing' could make for a really intense and dark fanfiction. The struggle between the two species in a shared world would be full of drama and action.

One idea could be a battle between the forces of Hellsing and some unique threat from the Alexandee universe. Maybe the Hellsing crew has to deal with a powerful magic user from Alexandee who is causing chaos in their world.

One idea could be that the wizards in the Harry Potter world discover the existence of the Hellsing Organization. Maybe Harry and his friends end up teaming up with Alucard to fight a common dark magic threat that is beyond what the wizarding world alone can handle.

The different universes that can be combined in these crossovers are also a big draw. For example, if you cross Alucard with a character from a superhero universe, you get a clash of different power scales and moralities. His dark, brooding nature against the more upbeat and heroic characters can lead to great storytelling. Also, exploring how his vampiric abilities work in different settings adds depth to the fanfiction.

Perhaps Ultimate Gohan could cross over into the world of Star Wars. He could use his powers to assist the Jedi in their fight against the Sith. His ki blasts could be like a new form of Force power in that universe.

How about a crossover with the Hulk? Spiderman might be on a mission in a city when the Hulk goes on a rampage. Instead of fighting the Hulk directly, Spiderman has to figure out a way to calm him down or lead him away from the populated areas. Along the way, they could encounter some other villains who are trying to take advantage of the situation, and then they end up teaming up to defeat the villains.