Today, while teaching a new driver a few of the basics, I had her pull to the side of the road to teach her how to use a reference point to aim while bringing the car to the curb (to get within the specified distance for parking).
While we were there I was teaching her about the right hand mirror ("Objects In Mirror Are Closer Than They Appear"). I explained to her what was different between the two outside mirrors and explained how the driver's side mirror is an exact reflection of what her eye sees, therefore she can accurately judge distance in that mirror. I then asked her if she could accurately judge distance in the passenger side mirror. She said "No". I told her, YES, you CAN. Would you like to learn HOW? She looked at the mirror, looked at me and said: "By pushing in on the middle of the mirror to make it flat?" When I reminded her that the mirror was GLASS, she hid her hands in her face and had a good belly laugh at her own expense. I had to join in. Now, this one is a joy to teach, and is one I would consider above average of what we see walking through the door to "learn".
So, I go back to the office and share that with one of the guys at the office, he roared with enjoyment. I went in and told the gal in the office what was said, and she looks at me and says: "You mean you can't do that?" When I reminded her of it being GLASS, she had her "Ah-HAA!!" moment of embarrassment too.