On my take-home final exam, just for fun, I included an extra credit question: "What is the secret code?"
I gave out the code on the last day of class, as a bonus for anyone who was there. It turns out that every student was there.
Some students missed the question. I have no earthly idea how they managed this.
Some students not only missed it, but made up their own code. Predictably, most of these students guessed the Konami Code. Except that -- get this -- they got the code itself wrong. I seriously considered giving negative points for this question in such a case, as penalty for defiling the memories of my youth.