Fandom fiction

There is a sub-genre - virtually exclusively in the hands of amateur authors posting to free story sites - of using famous characters from TV, film or written work and using them in a tale. 

There are several levels of psychology going on:  particularly in the world of spanking fiction. 

The easiest one to understand is that the author does not have to spend any narrative on setting up who the characters are, and how they are supposed to interact.   If you should elect to have Hermione Granger subjected to corporal punishment by Professor Snape (a tale that really exists on one forum) you do not need to spend time on descriptions or motives.   Your fellow Harry Potter fans know exactly who these two are, and why Snape would wish to inflict grievous damage to Miss Granger's hind-quarters.   However, you need to keep the tale posted only to some rather obscure site - J.K. Rowling's legal team would have no problem in swinging into action if they had a case you were making profit from copyright infringement.

But if you are safe from legal jeopardy, then it is just a matter of tweaking these pre-set characters to react they way you want.   In Book One itself, Hermione (with good intentions) did set fire to Snape's cloak.   In your tale, you might add that she later discovers that the ancient student code of corporal punishment for students - who cause actual bodily harm to staff members - was not included in the re-write.  That student law is still valid, despite the intent to repeal it.   Being that sort of girl, she demands that Snape follow the rules exactly as written.   You could even give Professor Minerva McGonagall a serious frown as she warns Hermione that the pain will soon fade, but not the memory that Snape will have seen her bare bottom.   See how easy it is!

The second theme is that you can fantasize about just anybody, and make them do your bid and call within the confines of a fandom piece.   Perhaps you think that Haley's mother should have taken a hair brush to her rump before now.   Voila - in your tale that is exactly what happens.   And when you watch all future episodes of that TV comedy series, the relationship of those two onscreen figures will, in your mind, be tempered by that good hiding Mom once gave her teenage daughter.

For the readers of fandom fiction, their motivation is less obvious to me.   Full disclosure - I do not enjoy reading fandom fiction.   But I can make some guesses.   Once the book, film, series is over, then there will be no more from that source.   So it is just great that some other sources take over to explore what and how your favorite characters continue after the "official" media is done with them.   People go to, for example, a Harry Potter fandom site for the sheer delight of new thoughts and ideas being expounded - provided that all of them stay in role forever.    Try to explore Snape's feminine side, and you might find you have become most unpopular on the site.

So fandom fiction gives us rapid access to existing personae and lets them follow our script, provided they stay in their original roles.   A not total waste of time, but you should only write stuff for sharing it with fellow enthusiasts, and for free.    Having said that, if your piece gives you a fully fledged outline for a professional piece, all you have to do is rewrite it with brand new characters.   Granted, they will need fleshing out:  but all the hard work is already done.    For a wordsmith, this is going to be one of those easy-peasy assignments.