There is a moment when you see something incorrectly - it may have passed by too quickly or you were distracted. Sometimes that glimpse gives you an impossible or improbable scenario. An item on a porch cannot be what you saw, or a utilitarian sign seems to have exotic alien insignia.
For a moment our furthest-fetched imaginings are real in an unintentionally playful and joyous expansion of perception...of what can be. Something similar happens when we make art.