Back when AS/400s were AS/400s, I made a little tool to help the operators run a long process at night. I felt playful and left an easter egg: on Fridays the 13th, it would work as usual, but display a skull and bones with blinking red eyes while doing it.

It seems that Fridays the 13th are rarer than I estimated, because months later my boss woke me up at midnight because the operators had woken her up because it was the first time the egg was triggered. In hindsight, it was a foolish thing to add since this was a bank. Fortunately they took it with good humor, and even kept the easter egg to scare new people.

I suppose NASA is more formal than a bank, so they only let you fool around with the comments.