Mommy, why can I only see where I am? (This one took me awhile to understand, but it became a good lesson in imagination and empathy.)
Mommy, what makes freckles come out from the inside of people? (Skin is a fascinating organ, you know.)
Mommy, what is the little thing that's like a penis in my private place? (!!!!!)
Mommy, how come bones bend? (They don't! You have joints! This was a blessedly easy one to answer.)
And that is just a sampling. Whew. I'm exhausted.