We had the other end of the PT experience. One morning when DD was just under 19 months old she announced one morning that she was done with diapers. She had zero accidents that morning (bizarre!!!) so we ventured out to the park and when we got home I was distracted unloading stuff from the stroller and then came in to find her sitting on the potty but her pants were still on and rather wet. It was the only accident that day. We convinced her to wear diapers at night for a few days but since she was dry every morning that ended quickly. It was quite surreal.
