I'm not entirely sure as 'big cock phantom' is rather an odd and unclear term. Fanfiction usually involves creating fictional stories based on existing characters or universes. But without more context, it's hard to say specifically what this particular 'fanfiction' might be about.
No. Given the rather strange and unclear nature of the term 'big cock phantom', it's highly unlikely to be a popular genre. Most popular fanfiction genres are based on well - known franchises like Harry Potter, Star Wars or Marvel, and they have more common and relatable themes.
No. It is not a popular mainstream genre. It seems to be a very specific and rather niche concept that is likely only popular among a very small group of people who are into creating or reading very particular and unique fan - fictions.
I'm not entirely sure specifically as it could be a very niche or made - up concept in some fan - created stories. It might involve a fictional harem situation with some sort of phantom - like elements, but without more context it's hard to say more.
No, it's not appropriate at all. This kind of content is not suitable for public discussion or sharing. It goes against basic respect for others and the values of a healthy society.
Sharing such stories is highly inappropriate as it involves private and often vulgar sexual content. We should respect the boundaries of privacy and propriety in society.