One possibility could be that the Molecule Man's powers somehow disrupt the magic in the Harry Potter universe. Maybe he accidentally alters the molecular structure of Hogwarts, causing chaos among the students and teachers. Harry and his friends would then have to figure out how to reverse the changes and send the Molecule Man back to his own dimension.
The main antagonist could be an evil version of the Molecule Man. Maybe in his own dimension, he was corrupted by power and when he enters the Harry Potter universe, he wants to take over there as well. He would use his molecular manipulation powers to create all sorts of disasters, like turning the Forbidden Forest into a deadly, mutated place. Harry and his friends, along with the good - natured Molecule Man, would have to fight against this evil version.
I'm not aware of any official 'Harry Potter' fanfic with such a title. 'Harry Potter' fanfics usually have more positive and creative themes that are in line with the general spirit of the original series. Using inappropriate or vulgar terms in fanfic titles is not in line with the good-natured nature of most fan communities.
Some writers might give him a long, white beard like Dumbledore had, to show his age and wisdom. His hair could be completely gray or white, and his face might be wrinkled from years of stress and adventure.
One interesting storyline could be an old Harry Potter looking back on his adventures and sharing his wisdom with the new generation at Hogwarts. He might tell tales of his battles against Voldemort in a more nostalgic way, and how those experiences shaped the wizarding world today.
Well, it's unique because it focuses on a character or aspect that isn't the main focus in the original books. It can show a different side of the wizarding world, like different relationships or hidden corners of Hogwarts.
Well, just based on that title alone, it's difficult to determine its quality. There are so many aspects that make a Harry Potter fanfic great. For example, it could explore new relationships between the characters, or create exciting new magical adventures. But we don't know if 'skull is harry potter fanfic' does any of those things. So, it might be good, it might not.
Sure, but it depends on your specific criteria for 'good'. Some might consider a particular fanfic good based on plot, while others might focus on character development. So, it's a matter of personal preference. But you should be able to find something that meets your expectations with some effort.
I'm not sure if it's common. There are so many different types of fanfics in the Harry Potter fandom. Some focus on relationships, others on new adventures. While metamorph - related ideas are interesting, it might not be as common as, say, romance - centered fanfics.