From glaringimission, 5/20/10
I think a lot of my writing is accidental, to tell you the truth. I do generally have a plan when I write, but I frequently deviate from it as ideas come to me. I know the process is different for everyone, that's just how I do it. As far as making a mistake in my writing and then using it, I can think of one significant example: Gruda.
Originally, the dragoness Gruda Tyrsdaughter was supposed to be subservient to Xyus, the dragon she's paired with romantically. The first time I described Gruda in the book was when Yomiko walks in on her giving Xyus another rune-tattoo on his scalp. I accidentally described her as 6ft4 instead of 5ft4, which would make her shorter than Xyus and only slightly taller than Meg (who is 5ft3). When I read back through and hit that description, the thought of her towering over Xyus (and most of the other characters in the book; Garrett is only six feet tall) was just too memorable to correct. I don't know if I did it subconsciously or not, but through the story that followed Gruda was less Xyus' pet and more owner. While Xyus was a mad dog willing to tear into anyone he found, Gruda was a cold, calculating bitch holding the leash. Gruda became a much better character as a result, and far more terrifying because of her size.