How’s this for a gem? When my wife and I were sending out wedding invitations a year ago, we wrote the sendee’s address on the front and affixed the stamp to the top right of the same side (of course), but stuck labels with our return address on the flap to seal it. As was later explained to us by the USPS, apparently someone that day ran our 50+ cards through the machine backward so that the bar code was on the wrong side, then the mail man, somehow not catching this, delivered every single card back to our house. He never even questioned why we were getting so many of the exact same cards delivered at once. This was in Malden, MA which might explain the story right there.