In chapter 14 of Herman Melville's The Confidence-Man, the narrator intrudes to tell the readers not to blame the author for creating an inconsistent character, for in the real world, most people are inconsistent. The narrator then shares some reflections on human nature and on characters, in fiction and reality.
And in chapter 13 of John Fowles' The French Lieutenant's Woman, the narrator intrudes to admit he doesn't know what his characters are thinking and that he can't fully control them. He then shares some reflections on writing, reading, and human beings in fiction and reality.
It's rather clear that metafiction is not any post-modern development, even if it is post-modern writers who relish in it. The seeds can be traced far back, at least to Cervantes in the novel. And so too have many novelists swung it back to blur the lines between fiction and reality. I leave you with a wonderful passage from Fowles' 13th chapter:
"But this is preposterous? A character is either 'real' or 'imaginary'? If you think that, hypocrite lecteur, I can only smile. You do not even think of your own past as quite real; you dress it up, you gild it or blacken it, censor it, tinker with it...fictionalize it, in a word, and put it away on a shelf--your book, your romanced autobiography. We are all in flight from the real reality. That is a basic definition of Homo sapiens."