One common theme is friendship. Fatgum is often depicted as a very friendly and approachable character, so fanfics tend to explore his relationships with other characters in terms of friendship. Another theme is mentorship, as he is a mentor in the BNHA world.
One popular 'bnha fatgum fanfic' is 'Fatgum's Big Heart'. It focuses on Fatgum's journey of mentoring a young hero. Another great one is 'The World Through Fatgum's Eyes' which gives a unique perspective on the BNHA universe from his point of view.
Some characters in bnha scary stories are unique to those stories. These new characters are often created to add to the spooky or suspenseful atmosphere. They might have really strange or terrifying quirks that we don't see in the main series. For instance, a character with a quirk that allows them to manipulate shadows into terrifying shapes that can attack people. So, in many ways, they are different from the characters in the main series.
Yes, the Bnha manga has finished. The final chapters wrapped up the plotlines and brought closure to the series. It's been quite an adventure for fans.
Some powers might need to be toned down. For example, Todoroki's ice and fire powers could cause a lot of damage in the real world. He'd have to learn to control them more precisely so as not to cause destruction. And some powers might be more useful in unexpected ways. Uraraka's zero - gravity power could be used for things like helping with construction or moving heavy objects in a safe way.
It could be integrated through a quirk accident. Maybe Izuku is exposed to some strange energy during a battle or an experiment gone wrong, and this gives him the ability to see ghosts. This would be a believable way to introduce the concept within the context of the BNHA world's science - based quirks.