Family dynamics is a huge theme. Given that the Umbrella Academy is all about a dysfunctional family of superheroes, fanfics often expand on this. They might show how the siblings deal with their past traumas together or how they try to become a more functional family unit. It can be really heart - warming or heart - breaking depending on the story.
A really interesting fanfic is 'Time - Twisted Umbrella'. In this one, the timeline gets all jumbled up, and the characters have to figure out how to fix it while also dealing with their own personal issues. It's a unique take on the whole concept of the Umbrella Academy and its connection to the Marvel universe.
Some characters would be shocked. Allison, for instance, might be taken aback by how some fanfictions explore her power in different ways. She could be both fascinated and a little bit worried about how fans perceive her use of the 'I heard a rumor' ability.