I was working at a doctors office while going to (and still attending) college. Everyone knew my major was computer science which meant everyone came to me when their browser didn't open. The night before April fools I turned off all of the wireless mice and used a label maker to print out "April Fools" on the bottom of each mouse next to the "on/off switch." This prank is miniscule in comparison to others here I'm sure, but the next day was my day off and I had the entire office calling me asking me to come in and fix it. "Taco what do we do???" They frantically asked. And so I very calmly said, "Did you turn the mouse over?" And hung up.