Some characters might be flattered. They would see it as a sign of their popularity. Archie, being a central character, might feel honored that fans are so interested in creating new stories around him.
Most likely not. In the Umbrella Academy universe, there's no indication that they are aware of the fanfiction world that exists in our reality. They are too busy dealing with their own apocalyptic problems and family drama.
Some do, but not all. It depends on how deeply they're into the franchise.
Happy Hogan might be entertained. He has always been a supporter of Tony Stark, and seeing the various fan - made stories about Iron Man would be like getting extra stories about his boss and friend. He might even share some of the more hilarious fanfiction with his co - workers.
Some characters might be excited. They could enjoy seeing new adventures created for them in the fanfiction.
They may find it strange. Since RWBY has its own unique plot and themes, Jackass fanfiction is so different. They might not fully understand the humor or the point of it.
On the other hand, characters like Sandy might be a bit more reserved. He might not fully understand all the wild ideas in the fanfiction at first. But as he watches or is exposed to it more, he might start to adapt some of the positive elements. For instance, if the fanfiction has a new way of using dreams to solve problems, he might consider incorporating that into his own methods.
Characters could be either excited or offended. If the crossover fanfiction portrays them in a positive and interesting new light, they might be excited. But if it misrepresents them or makes them look bad, they could be offended. For example, if a heroic character is made into a villain in the fanfiction, they would not be happy about it.
Well, many of the Shadowhunters characters have strong personalities. Magnus Bane, with his flamboyant nature, might find it hilarious. He loves the idea of being a center of attention and the creativity of fans in fanfiction would be right up his alley. But characters like Luke might be more indifferent. He's more focused on the practical matters of keeping the peace between the Downworlders and Shadowhunters. Fanfiction about him might not be on his radar at all.
Ruby would be startled by the Saw fanfiction. The extreme and often cruel scenarios in it are not something she's accustomed to. Weiss would have a strong negative reaction. She values grace and beauty in stories, and Saw fanfiction lacks that completely. Blake would try to empathize with the characters in the fanfiction who might be victims, but overall find it a difficult read. Yang would be quick to dismiss it, stating that it's not her cup of tea and that she prefers stories with more action and heroism.
Personally, it's a rather strange concept. Fanfiction often takes characters in unexpected directions, but this seems a bit out of the ordinary. However, everyone has different tastes in fan - created content, and as long as it's within the boundaries of legality and respect, it has its place in the fanfiction community.