I try to avoid other customers when shopping, just because I don't need the hassle. But I have had some funny encounters with female sales clerks. I bought some panties in the girls' department at a Sears once and was checked out by a cute young female SA. Trying to make small talk and put me (and herself) at ease, she first asked me if I had a daughter, which I didn't quite hear, then asked me if they were for my daughter. I answered "yes", sheepishly, then I saw the wheels turning in her head as she figured out that I was too young to have a daughter big enough to wear a that size (18-1/2), and that meant they were for...me. She blushed bright red and tried to cover her embarrassment by talking about her date that night. It was sort of cute. And as someone else mentioned, I sort of enjoyed the humiliation.
Another time, I was doing the same thing in another Sears, and the young female SA gave me the opposite reaction...she thought I was actually buying for a daughter, and said to me, "I bet this just makes your day, doesn't it?"--as if I'd been sent out with a list and a 6-pack of panties was on it. She was sympathizing with the humiliation she thought I was going through. I thought, "you don't know how right you are", at the way I actually felt.