I've had others like that. An advertisement for a Hannah Montana concert led to me reminiscing about my own childhood aspirations and the games I'd invented around Alice in Wonderland (we had a wonderful embankment in our garden that made for a perfect tumble-down-the-rabbit-hole sequence). Within a day I had an entire novel outlined involving crossing over to another world.
My not-so-pleasant experience at a hotel in Torquay led to an idea for a comedy a la Fawlty Towers, but set in a family residence. My characters had other ideas when they started killing each other. That book was a mess and I eventually "frogged" it (a knitting term I love, meaning to rip all the stitches out and reclaim the yarn to start again from scratch). But I was drawn to the premise of a dysfunctional family with layers and layers of secrets, and the moment I saw a photograph of a manor house that just had to belong to this family, the pieces clicked together and I started writing.
My most bizarre inspiration was from a dream. I've written about this one before. The dream involved a pygmy hippo, but in the book the hippo is simply a dog. Despite it's psychedelic beginnings, this story is my most "normal", with no elements of fantasy or magical realism.
I'm being deliberately cryptic, I know. None of these books are published yet because I have editor's block. And a distinct lack of time these days. I'm working on both those issues.
What about you? What inspires your stories? Do you sit down to deliberately craft ideas, or do you wait for flashes of inspiration and grab for the nearest shopping receipt or sheet of loo paper to write them down?