Via Dustbury, I was led to this wonderful paper on the phenomenon of the Mary Sue character, both in and out of fan fiction: Too Good To Be True: 150 Years Of Mary Sue.
What turned it into a lengthy and fascinating time sink for me is that I've never watched, for instance, Buffy the Vampire Slayer, or Highlander: The Series (or any of the Highlander movies apart from the first, actually, since There Can Be Only One,) or the various Star Trek spinoffs after the one with the bald guy as captain, so every time I encountered an unfamiliar character or series, I turned to that handy black hole on the internet: Wikipedia.
And it is flat amazing the time and effort fans of these various shows have put into their respective chunks of Wikipedia. There is probably a larger and more detailed web of articles on the TeeWee series Highlander than there is on the actual Scottish Highlands. It is just unreal. Literally.