Another great crossover could be with 'The Boys'. In this scenario, the Umbrella Academy would be thrown into the world of corrupt superheroes. They would have to navigate the complex politics and power plays while also trying to stay true to their own values and not get caught up in the dark side of superhero - ism.
One idea could be exploring what would happen if a new member joined the Umbrella Academy. Maybe a time - traveling superhero from the future who has knowledge of a great threat coming. Another could be a story where the members lose their powers and have to rely on their wits and teamwork in a completely different way. For example, dealing with a powerful enemy who can nullify powers.
One idea could be creating an OC who has the power to manipulate time in a different way than Five. For example, they can freeze time for specific objects or people while the rest of the world continues as normal. This would add a new dynamic to the Umbrella Academy's adventures and interactions with the timeline.
One idea could be to have characters from different universes meet under the Resh umbrella. For example, a character from a fantasy world and a character from a sci - fi world could find themselves taking shelter under the same Resh umbrella during a strange interdimensional storm.
A great plot could be that The Handler gets amnesia. Losing her memory, she has to rely on the kindness of the Umbrella Academy members she once opposed. This forces her to see them in a new light and also makes her question her own actions. It could lead to a journey of self - discovery for her within the world of the fanfiction.
One common theme is the clash of different powers. For instance, when the Umbrella Academy crosses over with another universe with superpowered characters, there's always a comparison and sometimes a struggle between different types of powers.
A possible plot idea is that Klaus discovers that his ghost - seeing ability is not just a random power, but part of a much larger, supernatural plan. The ghosts he sees are actually messengers from a different dimension, and they are trying to guide him to save both his world and theirs. Also, the fanfiction could explore a plot where Klaus' relationship with a particular ghost deepens into a strange friendship. This ghost has the ability to enter the dreams of the other Umbrella Academy members, and Klaus has to use this to his advantage to solve a mystery within the academy. Or, there could be a story where the ghosts start to disappear one by one, and Klaus has to race against time to find out what is causing it and stop it before he loses his connection to the spirit world completely.
Another plot could involve Five getting sick due to some side - effect of his powers overusing them in a short period. As he gets sicker, he starts to lose his memories of different timelines he has visited. The story could then focus on his journey to regain those memories with the help of his siblings.
Perhaps the fanfiction could be about a baby that is the result of a time - travel accident within the Umbrella Academy world. The baby has a mix of powers from different eras and the academy members have to figure out how to deal with this unique situation. They might have to teach the baby how to control its powers while also protecting it from those who fear its abilities.
Definitely Five and Tony Stark. Five is a time - traveling genius, and Tony is a brilliant inventor. They'd either be at each other's throats competing to come up with the best plan, or they'd team up and create some amazing tech. Another interesting pair would be Klaus and Thor. Klaus's laid - back, drug - addled attitude would be a stark contrast to Thor's godly seriousness. It would be hilarious to see how they interact.
Definitely Hazel and Cha - Cha from the Umbrella Academy with the Penguin. Hazel and Cha - Cha are these deadly assassins, and the Penguin is a mastermind criminal. They could form an unholy alliance to take over Gotham or something. Then there's Klaus again. He could be paired with Alfred. Alfred has this calm, collected demeanor and a wealth of knowledge. Klaus could drive him nuts at first, but then they could end up having some deep conversations about life and death. And Diego might be an interesting match with Red Hood. They both have a bit of an anti - hero vibe, and their different fighting styles could lead to some intense battles or reluctant partnerships.