I forget if Eco mentions this, but "Casablanca" is a lot like Shakespeare re:insertion of dialogue/verbiage into common parlance. The Epsteins and Koch managed to write phrases like "round up the usual suspects" or "this is the beginning of a beautiful friendship" that appear just as often in the English language as "smells to high heaven" or "cruel to be kind" do. Either way, I'm usually prone to trust Eco unless I can find something I really, really disagree with, because he's one of the few people who can talk semiotics while still making sense, and who can talk about pop culture without going through that pleading "no, really, we -should- discuss pop culture!" phase.