Oh God, I'll never forget it as long as I live.
My oldest son was three years old and really struggling with pooping on the potty. We were doing a lot of cheerleading and bribing, but nothing could convince him to make the transition from pull-up to potty.
Our house was on the market at the time and I had an agreement with the realtor that she would always call first before stopping by to show the house to potential buyers. Well, one day, she called and said she was 10 minutes away and wondered if she could stop by with some clients who she thought would LOVE my house. My 3 month old baby was napping and I explained that I didn't want to wake the baby and leave, so she would have to show the house while we were there.
I was racing around like a chicken with my head cut off trying to stash clutter and tidy up when my son announced that he really had to poop. (Of course, right?) I was tempted to tell him to just go in his pull-up, but I didn't want to confuse him, so I popped him on his potty and told him to call me when he was done.
Two minutes later the doorbell rang. As I was welcoming the realtor and the potential buyers into my foyer, my son came walking down the hallway toward us, totally naked from the waist down and holding a fresh turd in each hand. "Mommy! I did it! I pooped on the potty!" he exclaimed with pride. "See?"
The realtor started backing toward the door and stammered, "Oh, we'll just reschedule when you're not so busy. Sorry to intrude!" Needless to say, that family did not buy our house.