[quote=Dynamics]
They were based on inspirational experiences of the author.
[/quote]

But the story that came out of it was sufficiently creative enough to be nearly completely original. I mean, I got my Shapers idea from a dream, and Paper Sky from a song. It evolved into something much more. The fanfictions I referred to were inspired by MLP, and in fact took place in the MLP universe, but they evolved into something much more. MLP is very lacking in detail about mechanics and the world as a whole, and thus is breeding ground for countless original ideas. For good fanfics, the source material is simply a base from which they expand to something nothing short of an original work, save for the fact that it has the location Equestria and has ponies.