This joke was attributed to Achilles Varzi, where I heard it from Jacob Barandes on the Robinson Erhardt podcast:
A ufo visits a philosophy conference. A bright light shines down, all the philosophers look up and they hear a voice from the aliens saying earth has been randomly selected to receive the answer to any single question that earthlings have but they only get one question and one answer before the aliens leave never to return. The aliens say they will give them one week to deliberate before they return.
The philosophers of course begin debating amongst themsevles. "Well, we only get to ask one question, what is the most important question we could possibly ask? What if we ask something about meaning and the answer turns out to be not all that interesting and we lose our chance." "Should we ask about the nature of being or the nature of laws or what it means to live a good life or what are the ultimate laws of the universe or the unified laws of the universe or the best mathematical axioms." They go on debating and debating and debating. Finally they realize they are never going to come to an answer and even if they came to a consensus they wouldn't infact know that it was the best question. And they were worried that a century from now they might realize there was a better question they should have asked.
So they hatch a plan. They decide that they are going to ask: What is the two element set that contains as its first element the best possible question we could ask and contains as its second element the answer to that best possible question? They feel very proud of this, they even came up with this two days before the deadline. They decide they are just going to have fun and party the rest of the two days.
On que, the aliens return and the light comes down, the chair of the conference is ready and the alien asks: "Ok, now you can ask your question, what is it?" The chair of the conference stands up, takes a deep breath and says "Here is our question: What is the two element set that contains as its first element the best possible question we could ask and contains as its second element the answer to that best possible question?" Impediately, the aliens respond and say "Excellent! What an excellent question! Here it is: In the first element is 'What is the two element set that contains as its first element the best possible question we could ask and contains as its second element the answer to that best possible question?', and the answer in the second element is 'The question what is the best possible question we could ask and what is its answer?'" and with that the aliens fly away never to return.
What a great joke and a humorous reminder that we cannot gain deep and meaningful truths on technicalities or tricky questions.