Fitful Creativity

My creative impulses have been strong recently. I cranked out a short story the other day and then restarted work on my novel. Lying in bed last night half-lucid, I thought of a really good idea for a story starter. It wasn't a plot, merely an amusing device that would have been a unique kernel to develop one. But even as I lay there, I knew I would not remember it in the morning, and I don't. It had something to do with reversing a paradigm in a way that was funny. I feel like there is a word for that, but I can't remember that either.