I don't know the capital of every country in the world, nor do I think I *should* - but this is still fun:
When I was little, and couldn't sleep, Mom suggested I list every single state in the US, alphabetically. If I ever realized I'd missed one, I had to go back and start from the beginning. I don't think I made it to Wyoming.
I found myself, as I passed San Bruno Mountain today, where the endangered Mission Blue butterfly lives, "There are Mission Blues on San Bruno Mountain, but the California dogface butterfly is our state butterfly. Why do I know that? I don't know. I just do."
It's the sort of useless thing that helps me paint a picture of the world when people talk about it. It's a piece of the whole puzzle.