Aside from the original animatiopn/manga/story as a basic structure for
  the fanfics created, are there any othe sources of inspiration for the
  fanfic writers?  Anyone care to share their feelings?

I'm not a fanfic writer in the traditional sense, but I'll tell you
about my insp. anyway:

1. Gags.Comedy bits which I think of and adapt to charaters.

2. Paralells, certain paralells in shows/comix. You ever notice hpw much
Nabiki's hair looks like Velma's?

3. Jack Benny. Marx Brothers, Amos and Andy, ect...

Noah "What does this button do?" Bellamy