Jon M. Obermeyer
Usually a quotation from another writer. Joan Didion has a quote about the prevalence of mattresses atop cars in the South, so now in my head I have a poem or a short story called "Mattresses." It's not plagiarism; it's a shove from that other writer, playful and insistent: "go on, do it!" Come to think of it, writing about plagiarism might be fun.