That's awesome, EUOL.
Okay, here's mine. Let me establish the scene for you: My wife and I live in the same condo complex as her brother and sister-in-law, so we often go up there to hang out while our kids are asleep (taking the baby monitor with us). On one particular evening my father-in-law was visiting, and we were all upstairs at the other house tolerating his presence--nobody likes my father-in-law.
So eventually we hear 5-month-old crying on the baby monitor, so we go downstairs to change his diaper and whatnot. While we're down there we start mocking my father-in-law pretty mercilessly, as he'd been slightly ruder than normal that evening. We comment on how he's a big bully, and drop a few comments regarding his intelligence, and right about then we realize that we're saying all of this--you guessed it--less than three feet from the baby monitor.
As you can imagine, we were almost too frightened to go back upstairs. We literally thought that all peace in our lives had just ended. We finally got the courage to go back upstairs, and eralized that they had unplugged the monitor as soon as we left, because the crying baby was drowning out their movie. They hadn't heard a thing, and we breathed a profound sigh of relief. Sufffice it to say, we try to be a lot more complimentary of my father-in-law these days.