I've just finished reading House of Leaves in a book club.

One of my favorite bits from the House of Leaves is that all through the whole thing there's all these footnotes and they're basically all just made up references to random academic journals or speeches or things that don't exist. And then out of nowhere in one of the citations, they are talking about the Frenchman Pierre Menard and mentioning it as fact, someone who is attempting (succeeding) to recreate Don Quixote.

This is actually a Jorge Louis Borges quote and a piece of one of his writings, which is completely unattributed inside of the House of Leaves footnote. It's like they are citing the fictional book, not the actual Borges book, but they didn't even cite the fictional book. Maybe both stories are set in the same universe.