JDuncan has left a new comment on your post "Writer's other worlds":
"In this same vein, and out of curiosity, is there anything out there were the
m(ain)c(haracter) discovers they are actually a written character in a novel and then interacts in some fashion with the writer in order to alter the story?"
The only one of these that comes to mind was the Will Ferrell movie STRANGER THAN FICTION, but it doesn't appear to be based on a novel.
However, I received a pitch for one of these at the WD Pitch Slam, so perhaps I'll have one of these to sell shortly.