There's a "Do you poop" thread on the DL forum that has jogged some memories for me and inspired this thread topic.
I remember quite a few times from childhood where I didn't actually have a poop accident, but obviously didn't take the time to wipe properly, if at all, and suddenly it's bath or bed time, I'd get undressed, and find my underwear badly stained.
My younger brother did it to occasionally. When we were little we often bathed or showered together, and we would undress in the bathroom, and his knickers would be dirty.
I remember mum used to hate it! She would get so much more upset about us not taking the time to wipe properly, and would be madder than if we had a real accident.
There's something very little about having dirty pants, even if you haven't had an actual accident.
Anyone else used too, or still does find unexpected surprises when they get undressed?