When my ex said "oh shit the condom broke". Edit: Finally remembered a noteworthy one. Was at a zoo in the reptile section when we came to the Burmese Python pen. I saw 3 but the sign said that there were 4. Apparently there was a slight ledge right above the glass on the inside of the pen that the snake was on top of, and as I was up close to he glass looking for the 4th one its enormous back end slipped off the ledge and banged against the glass right in front of my face. My friends got a good laugh out of my reaction. I jumped like 5 feet.