We were going to be spending he entire day at the theme park and I told everyone to dress accordingly.  Our teenage son showed up with his newest designer sunglasses and was ready to go.   I asked him what he was going to do with them as I did not want to end up carrying them in my backpack after the sun went down.  He just told me not to worry as they were made for the dark.  That evening I discovered that he glow in the dark shutter shades.  This should have made him easy to spot except that there were so many other people wearing them.