My friend David Steffen wrote a piece called "The Quest Unusual" for the PodCastle flash fiction contest. His story was a humor piece, featuring a dragon in armor asking oblivious local peasants if they'd seen any dragons around, with the punch-line being the rural man's remark that there was no such thing as dragons. I couldn't get the image of a dragon-who-is-a-knight out of my head, especially once I realized that he would logically have to be looking for a knight-who-is-a-dragon, just for symmetry. I started out writing just a 100-word sketch for Mirrorshards, but that wasn't enough to exorcise the idea. I didn't want to "waste my time" writing an entire story because I felt like I was just riffing on David's concept. However, at the time, I was under a self-imposed demand to write at least one full short story every two weeks for a full year, so I finally just gave up and went for it, figuring I'd keep it for myself if it turned out rubbish.
Two days and seven thousand words later, with the story largely in its present form (I am both a binge writer and an incorrigible pantser), I realized that the concept *really* had legs. I sent the manuscript to David; because the story was largely inspired by his own, I didn't want to submit it anywhere without his permission. Initially, David was (understandably and thoroughly justifiably, I think) reluctant, and he told me I'd have to trunk the piece, as I'd expected. A few days later, however, he changed his mind, and asked only that I wait until he'd sold his flash fiction story. (He says he was worried that a glut of dragons-that-are-knights would drive demand down, making it a harder sell; me, I think you can never have enough dragons.) As you've likely guessed, David's piece sold quite quickly (you can read it at Daily Science Fiction's permanent archive), and so here we all are today.