Twins two years apart

I took Alyssa and Vivian out for shopping today. At one of our stops the cashier asked if the two girls are twins. When I told her that their birthdays are two years apart, her reaction was "Really? They looked identical other than one is a little bit shorter than the other." She said some very nice things about how cute they are and gave each of them a small bag of cookies. The girls were thrilled.