What are some great questions kids have asked you?

I was in the car with my 8 year old today and out of nowhere he asked me could all the people in the world fit in Ireland. I thought it was a great question. I obviously didn't know the answer and wouldn't look it up while driving but we went through some steps on how might we work it out, as it turns out we all would have a spacious 9 square meters each, I can't wait to discuss it with him in the morning. Have kids ever asked you a question that you though was super interesting or unusual?