I suppose the proper hackish definition is basically "a bug," but it's also an online fan fiction/fanfic epic that includes elements of anime such as Dirty Pair and other geeky topics. Full of angst and geek humor, it's probably the only anime-related fanfic worth reading. It's by the Eyrie Productions group, who also do Neon Exodus Evangelion, loosely based on the Evangelion anime. www.eyrie.net

Undocumented Features was one of the first anime fan fiction stories to hit the Internet, shortly after Larry Mann's Dirty Pair fanfic, Experiment 101-E. As such, it has had no small degree of influence over the subsequent anime fanfic scene.

Though not intended to be in the beginning, Undocumented Features soon became a perfect example of a shared universe setting...too shared; soon after the first couple of stories came out, the Eyrie Productions crew discovered everybody and his sibling wanted to write a UF story.

The Eyrie Productions website can be found at http://www.eyrie.net...not to be confused with The Eyrie, http://www.eyrie.org, Russ Allbery's personal homepage.