Henry Jenkins
in "Textual Poachers" includes a section about ten different ways a show can be rewritten as a fanfic.
1.
Recontextualization - Filling in the gaps in broadcast material and providing additional explainations for characters' conduct. See
Fan Wank and
Fix Fic.
2.
Expanding the series timeline - Either into the past or future. See
Continuation,
Prequel and
Backstory.
3.
Refocalization - Shifting attention away from the program's central figures and onto secondary characters (often women and minorities). See
Day in the Limelight and
Lower Deck Episode.
4.
Moral Realignment - Inverting or questioning the series' moral order. See
Deconstruction/
Deconstruction Fic,
Alternate Character Interpretation,
Perspective Flip,
Die for Our Ship and
Draco in Leather Pants.
5.
Genre Shifting - Telling stories different in tone and style from those of the actual series. See
Characterization Tags,
Dark Fic and
WAFF.
6.
Crossovers - See
Crossover and
Fusion Fic.
7.
Character Dislocation - Characters are removed from their original situations, and may be given alternative names and identities. See
Alternate Universe Fic and
Transplanted Character Fic.
8.
Personalization - "Mary Sue" stories, and stories that break the fourth wall by having characters interact with fans. See
Mary Sue,
Marty Stu and
Self Insert Fic.
9.
Emotional Intensification - Including the "Hurt-Comfort" genre. See
Hurt/Comfort Fic.
10.
Eroticization - See
Lemon,
Lime and
Porn Without Plot.
of course, these are the rules of fanfic. If you're a pro, just
stick 'em on a rocket. If you are interested in more ideas about writing fanfiction see
So You Want To Write A Fanfic.