A few months back, I was mostly dressed (underwear and forms) when a USPS mail carrier knocked on my front door. Through they door they said it was a registered letter requiring my signature, or I could pick it up at the Post Office after the 3-day weekend. I haven't had a registered letter in 10+ years. It was out of the blue and I had no idea what it was.
I threw on a robe, but I was clearly dressed when I opened the door. My black tights and flats were obvious, and I held the neck of the robe closed with one hand, which made my chest even more obvious. I was very nervous and fumbled with the electronic pad, and they eventually offered to sign an X for me. I handed back the pad, and before I closed the door they said "I'm sorry", and they looked like they really meant it. Since then I've been making a point to wave to the mail truck, and they always wave and smile, same as always.
It turned out to be non-urgent paperwork about a late relative's estate, but now that it's over I feel good about the encounter.