There’s only one thing more fun than the reaction that your coworker has when they return from a trip to see their desk, and that’s taking pictures of your hard work. Gizmodo took note and allowed me to discover this great display of bored and creative coworkers. My favorite is the Aluminum Foil, I’d keep it if that was my desk. I may need to get a NASA coffee mug to feel like I’m in a real space station.
At my old work we’d change desktop wall papers, screen savers, or my signature move: put a piece of tape over the eye of the optical mouse and lie in wait for your victim to return.