A strange thing is happening as I write. New characters are appearing out of nowhere and establishing themselves as vital to the story before I even know who they are. Does this happen to other writers?
For example, the main character in my story owns a bookstore. I had planned for her to have one employee who would play an informational role later in the story but all of a sudden a second employee has emerged and I see now that she will be just as important as the first guy but in a slightly different way. This unexpected character possess knowledge that no one else does and which will become necessary later on. If she hadn't created herself I would have had to go back and add her in later.
I guess it's good that my characters know their own story better than I do!