It was definitely top five before I learned this, but now? Wow.
Okay, so I've been reading the old Mark Watches threads on Princess Tutu, because that predates my involvement with the site. On the thread for Season 2, Episode 4 (episodes 7 and 8 if you're using the TV numbering), "Crime and Punishment," a user named Manuscriptgeek Googled the visible fragments of German text in the book Fakir is reading (the one that's had pages torn out).
It turns out the text is the description of The Neverending Story from the Amazon.de page, which is taken from The Book of 1000 Books, a collection of descriptions of important German texts.
Yeah, Fakir's desperate research? Is about metatextuality in literature, and he finds the story of a boy who enters a story and alters it with his powers of storytelling. And Autor is stalking him while he's doing this.
I believe my response can best be summed up as "holy flurking schnit."