Two of my favorite questions from my dd when she was a preschooler:
After finding out I was pregnant, "If I came from your tummy, and you came from your mommy's tummy, and she had a mommy, and her mommy had a mommy, then where did the first mommy come from?"
And another, "Dinosaurs were here before us but now they're extinct, right? So what what will be here after we're gone?"