#WritersCoffeeClub 13: What do you borrow from other fiction (or nonfiction!) genres?

First thing that comes to mind are the footnotes I borrowed from non-fiction (or Terry Pratchett). I started having them in #TheMindOnFire. It took so long to write it that I started to forget where I had that quote/fact/whatever from. I kept them after I was done since the whole thing was too long for a full author's note.
I re-used that strategy for the next two historical books although they're shorter.