Droppings - If you went outside and lay down on your back with your mouth open, how long would you have to wait until a bird pooped in it?
Random Sneeze Call - If you call a random phone number and say “God bless you”, what are the chances that the person who answers just sneezed? On average, not just in spring or fall.
Billion-Story Building - My daughter—age 4.5—maintains she wants a billion-story building. It turns out not only is that hard to help her appreciate this size, I am not at all able to explain all of the other difficulties you'd have to overcome.
Some questions answered via video on the YouTube channel: xkcd's What If? - YouTube
Randall Munroe also writes the webcomic XKCD which is great and has some fun math comics. My favorite comic is not mathy, but here it is just for fun: xkcd: Grownups
Good mathy ones:
xkcd comics can be kind of esoteric so there is an entire website dedicated to explaining the comics: explain xkcd