Thanks to Joy for sharing this:
After college, I took a job as a legal secretary at a law firm in Atlanta, GA. At the time, we all used Selectric III typewriters (PCs weren't around, and WANGs had just come on the market). We had a very nice, intelligent associate who had started about a month or so before April 1st, and although he was extremely smart at law, he was also a little too trusting and pretty naive. I clued the attorney I worked for into my plan, gave him some lines, and asked him to please call the associate and ask him to come to his office to receive a research assignment. The firm had a glass elevator that ran between the floors, and I sat at the very end of the building with a straight line of sight view of the elevator, so I could see when the associate was about to get off at our floor. As soon as the elevator door opened, I popped a smoke bomb into my Selectric typewriter and began to type madly (I typed about 100 wpm at that time), and acted intense and focused on what I was doing, while black smoke streamed up toward the ceiling! As he began walking toward me and drew near, I looked up at him and said, "Go on in. We have a Supreme Court brief due in just over an hour," and then looked down and kept going. He walked into my attorney's office and said, "do you see that?" My attorney answered, "yes, she's really fast, and in fact, we had to modify that typewriter because it wasn't fast enough for her to use her Dvorak typeball on it. Did you know that she can type 300 words per minute?" The associate was completely in awe - until my attorney started laughing.