One of the Qs was something along the lines of "Why do mirrors flip left and right, and not up and down?". Having heard the question before, I do know the answer, but still find it fascinating whenever it comes up, as it's one of those questions where the answer is completely obvious and entirely non-obvious at the same time (one of those kick yourselves when you find out the answer for not spotting it yourself type things).
The answer is, obviously (just to rub it in for those who don't know the answer already and like me didn't spotted it for themselves), that mirrors in fact flip front and back and not left and right. When you look at your reflection, your reflected left is still on your left and your reflected right is still on your right. The idea of these being flipped comes from the fact that your reflection is facing the other way and left/right depend on the direction you are facing whereas up and down don't.
I find it fascinating that the vast majority of people (including myself) pick up the misconception that mirrors flip left and right. Why is this? Is it due to discussing other people's left and right and considering our reflections as a separate entity? Do young children who are only just learning about left and right have this misconception?