This popped fully-formed into my head, and while I could write a story around it (or at least a scene), there is a certain standalone quality to it that I like.
The weirdest thing that ever happened to me was when I discovered that my superfluous third nipple was actually a fully-formed vermiform twin with telekinetic abilities and a hankerin' for cheese.
This now in my mind has a particular scene attached to it. It's a scene from a movie, shot in a bar with warm orange lighting, Diedrich Bader drinking a beer and telling this story to someone who hasn't been revealed yet.
If I were to explore deeper, I could root out where this stuff comes from inside my head, but I don't think I wanna. It's more fun just to write the stuff down and ride it where it goes.
You gotta admit, there's a hook there.