A couple of months ago, I returned from lunch to find that typing any key launched a random application. As I always lock my machine before walking away from it, my first thought was that a co-worker was playing a practical joke on me. As it turned out, the cause was random computer wonkiness. But just in case there's a need :), what's your favorite harmless computer practical joke? For example, would you alter host file entries to direct google.com to a random site or would you put tape over the optical sensor of a co-worker’s mouse?