I know I've posted this story before, but it soooooo fits this thread.
A long time ago, I worked for an insurance company. One day I was standing in front of my desk, talking with one of the marketing reps. We had pretty much finished our conversation and he was walking back to his desk, but still facing me and talking. Then the receptionist, an older lady who was the absolute epitome of class and grace, walked around the corner holding a pair of "Totes" - those rubber shoe coverings they make for men to wear in the rain. She said to the marketing rep, "Are these your rubbers?"
He looked at her, shook his head and deadpanned, "I never leave my rubbers laying around."
She nodded and said "Oh, ok." and walked back around the corner. He turned and looked at me, and the look on his face was priceless - kind of a "Can you believe I just got away with that?" look. Well, it's a good thing my chair was right behind me, because I literally fell back into it from laughing so hard. He did the same thing, and the two of us were laughing so hard we were practically not even breathing for the next 10 minutes or so.
Suddenly, the receptionist walked back around and said, "I know what you're laughing at. You should be ashamed of yourselves!" Which, of course, only made us laugh harder.