I had some Canadian customers use a Canadian two dollar coin to pay for some candy. She started to hand me the coin, then paused and said "You probably don't know what this is, do you?"
Are you fucking kidding me. I work in a retail store close to Canada. Of course I know about the damn Canadian Toonie.
There is a presumption with many customers that because they control a situation by making decisions about shopping, they are also omniscient. Few seem to realize that, in fact, I might know about the world. I also know alot about them (name, address, phone number, credit card number, purchase and return history, birthday, names of spouse and offspring, home color schemes, favorite food, food allergies, pet's name and breed, car make and model, location of vacation homes) while they often don't know anything about me other than my physical description, and maybe not even that.
Creepy but true.