I was in Paris ten years ago and turned on the TV in the hotel room. Besides "Cops" and "ER" dubbed into French, I came across a strange documentary that I eventually figured out was about Lovecraft entitled "Le Cas Howard Phillips Lovecraft." You can find it on Youtube. Kinda hypnotic.
Neil Gaiman talks about that in the piece. How Lovecraft’s characters just write and write till the horrible creature is worming his horned tentacles through the door...
I believe Jules Verne also did this in some of his novels.