Disclaimer: As much as I hate to admit it, Douglas Adams (may he safely hitch a ride home) owns HHG2TG, not me :(
The Hitchhiker's Guide to the Galaxy, the standard repository of all knowledge and wisdom, has this to say on the subject of fan-fiction: it is almost always literary suicide.
Fan-fiction (also known as fan fiction, fan fics, fics, and ficcies) is just that: literary works written by obsessees of a particular game, book, movie, standard repository of all knowledge and wisdom, and so on. It is not, however, something the amateur writer should trifle with. Despite this, countless intelligent life-forms insist on doing so anyway. Such actions usually result in catastrophe, internal hemorrhaging, and very bad grammar.
Fan-fiction today is, for the most part, pure garbage. It normally contains vast amounts of unnecessary swearing, and an actual plot is a very rare sight indeed. There are also certain characters nicknamed 'Mary-Sues' and 'Gary-Lous', who are always obscenely perfect, usually have names like 'Raven Serenity Moonfire Sparkleglow', and seem to exist for the sole purpose of annoying the reader. Most fan-fiction contains some form of slash, usually being between a very 'wrong' couple, ensuring that any reader is guaranteed to lose a few brain cells. In comparison, most fan-fiction makes Vogon poetry look good (see entry on 'Vogons').
Anyone who dares to write fan-fiction is either a half-decent writer, very brave, or very, very stupid, most probably the latter.
A/N: Yes, I know it's not perfect. I wrote it at about midnight a few nights ago after seeing the movie. Now, review, or I shall have to set my pet Ravenous Bugblatter Beast of Traal on you.
JuicyFrood, who know where her towel is