I'm not entirely sure as I haven't read it in detail. But generally, it might be about some sort of fantasy story involving a bishoujo (a cute girl character in Japanese media) and an ojisan (uncle or older man) in a novel - like setting.
I'm not sure who the main characters are exactly as I don't know this work well. But from the title, it seems that a bishoujo and an ojisan would be important characters.
I'm not sure which specific 'Mabel ghost story' you're referring to. There could be many fictional or local tales about a ghost named Mabel. It might be a story passed down in a particular family, community, or written by an unknown author.
A fanfiction might involve a love triangle between Human Bill Cipher, Mabel, and Dipper. Human Bill Cipher, with his manipulative ways, tries to win Mabel's love. Mabel is flattered by his attention but is also conflicted because of her strong bond with Dipper. The story could explore themes of jealousy, loyalty, and the power of true friendship as Dipper tries to protect Mabel from Bill's schemes.
Mabel was an elderly woman who loved to knit. Every day, she would sit on her porch and knit sweaters for the local orphanage. One day, a young girl came to visit her. The girl was shy at first, but Mabel's warm smile and kind words made her feel at ease. Mabel taught the girl how to knit, and they became good friends. Through their knitting, they brought warmth not only to the orphans but also to their own hearts.
One common theme could be mystery. Since it's a ghost story, there would likely be elements that are not easily explained, like strange happenings around the supposed hauntings of Mabel.
A 'bill cipher x mabel fanfiction' could explore a really strange and interesting relationship. Bill Cipher is this super - chaotic and powerful entity, while Mabel is full of charm and innocence. In fanfiction, it might show Bill trying to manipulate Mabel in his devious plans, or perhaps Mabel finding a way to outwit Bill in some unexpected way. It could also delve into how their different natures interact, like Bill's lack of morals against Mabel's strong sense of right and wrong.