I have heard that it can happen. That you can get so involved in the writing process that before you know it, you actually write a lot in a single sitting. But it never really happened to me until last night.
We had a mini-monsoon yesterday here, which apparently knocked down power lines and screwed up our Charter bundled stuff. Since we were without cable or the internet, and I wasn't sleepy, I decided to watch a DVD. I choose one of my favorites, Mystery Science Theater 3000 presents Werewolf. Then I remembered that I had a werewolf story brewing in my head. As the cheese-fest continued to play, I started getting a great idea on how to start the story in my head.
Luckily, I was in my office, at my computer, watching this DVD. So I started to write everything down as it entered the conscious part of my brain. In the span of an hour and some change, I wrote the first draft of the first chapter of this story. When I was done I was absolutely amazed! I had never in my life written a whole chapter in one sitting, let alone be happy with the concepts I put to 'paper.'
As I read over it, I was incredibly happy with two things. First, although somewhat inspired by the movie I was listening to, it in no way resembled its plot. The last thing I want is to write a story worthy of only copywright lawsuits and bad jokes. Second, I had managed to start the story off with action and introduce the key characters in the span of about fourteen pages or so.
I am well aware that I skipped an awful lot of description, and the character development is rudimentary, but I believe that it is a solid start. Best of all, it got me re-energized about my writing abilities, and I also wrote an additional 12 pages this morning for my main story. Now if I can just parlay this writing streak into a finished product...