In Alice in Wonderland, as Alice falls down the giant rabbit hole at the start, she keeps asking herself "Do cats eat bats?" And, since she can't answer it anyway, also "Do bats eat cats?"
A definitive evidence answer to the first of these two questions is now available right here.
Another famous riddle from Alice is the Mad Hatter's query, "Why is a raven like a writing desk?" Though both he and the March Hare profess to have not the slightest idea when Alice gives up, some decades later a Lewis Carroll fan (I forget who it was), gave what strikes me as the best possible answer: "Because there's a b in both."