i'm not sure whether this is a manifestation of A/S or the result of experiences common to those affected by it, but ever since i was very young - maybe five or six - i've written and latterly mused about this fictional character of my own creation, named Nadine.
i seem to remember a dream in which i met a girl with long, dark hair and accompanied by her brother, whose name was Kit, it transpired, who seemed to just appear in my kitchen, leading to this enquiry into who they were and probably why they were in my kitchen. in retrospect, it sounds like a paranormal encounter, with their just appearing there without any discernable purpose for their visit, but i don't think it even occurred to me in the dream that they might have been ghosts.
anyway, that dream is what i remember as the moment of Nadine's creation. i went on to write about her, endowing her with all the attributes i lacked and longed for: she was beautiful, asian, her family were affluent, she had the sibling i wanted. the material usually came in the form of reconstructions of day-to-day events in my real life, which illustrated her superiority to all around her - i don't think i was even above depicting other kids' nasty actions against me as hers. later, a kind of third central character, Nasima, emerged as a sort of 'hanger on' who desperately sought to befriend Nadine but whose dweebiness and poverty Nadine was characteristically contemptuous of. despite her being such a seemingly unadulterated b***h, her relationship with kit was one of mutual adoration which i knew at the time to be unnatural in siblings of that age.
i had a detailed vision of her physical person too, which would change when i became bored or inspired by something or indeed someone aesthetically appealing. whenever i got nice new clothes or admired clothes i couldn't have, i would picture Nadine in them.
as i reached adolescence, the writing became intermittent before stopping altogether in my early teens. but i still occasionally find my musing over the progression of her life had the character been continued, though only for brief periods. i've never reflected on this with anyone before, but i would be interested to read anyone's thoughts who has read this rather lengthly post! i don't care how f**** up you think it is, in fact tend to agree.

Well, it sounds to me like you're no less normal than any of the rest of us. Sounds like you have some interesting ideas. Don't choke them off. Keep writing.