While I was in Edinburgh, I had a kind of half-dream, which I remembered only dimly at the time, and don't remember at all now.
When I awoke from it, though the dream itself faded, it set me off musing, as I dozed and drifted towards full consciousness. I found I was imagining a possible scene for an as-yet-unwritten play.  Just the scene though - no story, no context, not even anything like a character. It seemed a nice scene though.
In due course I got up, and promptly forgot all about it.

Just came back to me, over a week later, so I wrote it down - purely as stage directions, no dialogue (since there was none in the scene I imagined).  I picked a character name out of the air, just to have a handle for the person whose actions I was describing - it could always be changed later.

Then I saved it, and, in naming the file, suddenly found that, entirely by accident, by randomly naming the character, I had also given the play a title, and what's more, a suggestion of a plot.

Rather chuffed.  I've no idea if I'll ever add any more to it, but it's genuinely the first time I've had a proper idea for a play that didn't immediately make me cringe.  Intriguing experience.