Shortly after I started my first programming job, I hung a poster in my office of some faeries flying around. As it happens, said faeries were topless. A few days later, I noticed that someone had cut little bikinis for them out of Post-Its. This was fine with me, so I left them there. Slowly, I noticed that the company librarian, who had previously been friendly, had become quite cold and standoffish. I didn't know what to make of it. Weeks passed. Eventually, I found out what had happened. The librarian had made the Post-It bikinis as a joke, but someone found out about it and, as a prank, left a note in her office telling her to stay out of my office and don't touch my things, and signed my name to it!
When I was in school, I was told in class that adverbs generally end in -ly. "Really?" I asked. "Are you sure? Ugly, lovely, friendly, silly, elderly, wily, curly?" Having anticipated this, I had memorized this list, waiting for the right moment, to see if I could pull it off. Sure enough, the teacher looked briefly confused, then said "Oh, right, it's adjectives that tend to end in -ly." And the class dutifully wrote it down.