Well, he might be shocked by how things turn out. He could see the fates of his friends, like whether Ron and Hermione's relationship endures. Maybe he'd find out if Hogwarts still stands strong or if there are new threats to the wizarding world that he hadn't anticipated.
At first, he may be in disbelief. But as he starts to understand what he's seeing, he could become solemn. He realizes the weight of the future and the responsibility he may have to shape it in a positive way. He might also feel a bit of fear, especially if he sees the loss of his friends or loved ones. But overall, his Gryffindor courage would likely kick in, and he'd start to think about how to face whatever the future holds.
He might also be a bit confused at times. Some fanfictions deviate a lot from the real events in his life. For example, if there's a fanfiction where he has a completely different upbringing, it would be strange for him to read about. He could also feel a sense of flattery that so many people are interested in his story and want to create their own versions of it.
He might be really surprised. Fanfiction often contains different interpretations of the characters and the story. He could be amused by some creative ideas, or perhaps a bit confused if the fanfiction goes too far from the original story he knows.
He could meet his future children, if he has any. They would likely be powerful wizards or witches with their own adventures. Also, he might run into the future versions of Hermione and Ron. They would probably be in important positions in the wizarding world, like Hermione might be a headmistress at Hogwarts or something.
He might meet the future versions of his friends like Hermione and Ron. Their children or grandchildren could be there, and they might have different personalities and magical skills compared to their predecessors.
I'm not sure specifically as I haven't read this particular fanfiction. It could be about a group of people from class 78 observing or experiencing future events in the context of the fanfiction's universe.
In the fanfiction 'Star Wars Watches the Future', it might involve the Sith Lords also having an interest in the future. They could be planning to manipulate events in the present based on what they see in the future. For example, Darth Vader might see a future where the Jedi are extinct and try to accelerate that process in the present, leading to a whole new set of conflicts and power struggles within the Star Wars universe.
If Harry Potter watches anime fanfiction, he could end up having some really strange dreams. The vivid and often wild ideas in anime fanfiction might seep into his subconscious. He might dream about flying on a broomstick while also having some of the crazy powers or going through the strange situations that are common in anime stories. Also, he could potentially get some new ideas for dealing with his enemies in the wizarding world. Maybe he'd learn about some creative strategies from the anime fanfiction he reads that he could adapt to his own battles against Voldemort and his followers.
Well, it could be really strange. Harry Potter is from a world of magic and wizardry, and Blackadder is a very different kind of comical and often satirical world. If Harry were to watch Blackadder fanfiction, he might be quite confused at first. He'd see characters and situations that are so different from Hogwarts and the wizarding world. Maybe he'd find the humor in it, or perhaps he'd just shake his head and wonder why muggles come up with such odd things.