I once worked on the design of video surveillance equipment, back in the days of dial-up modems. I put several Easter eggs into the code over the years. One was an insect that ran up the screen after 1 hour of complete inactivity by the operator. To test it I could trigger it by pressing one of the buttons 8 times in a row. When sales finally found out about it, they integrated it into their demos by saying that there was "one known bug in the system". Another was a screen saver that I added to the device. It was called "Rapid Vision" and an R would continuously morph into a V and back in different parts of the screen. Every 1000th morph, it would turn into the word "Hello" The last was when I left the company. I left an image of myself with mad animated eyes, that could be triggered by pressing a very particular (and highly unlikely) sequence of buttons on the keypad. I haven't done anything like since, apart from a simulated flashing LED indicator, on a GUI, that showed me that the timer interrupt was still functioning. It was labelled "GFL" (Gratuitous Flashing Light)