I love it when we meet new people and they will remark excitedly about the fact that my daughters are wearing matching clothing. The first question after that is usually to ask if we did it on purpose or inquire if it’s a special occasion. They are literally shocked when I then say that my girls have spent roughly 99% of the 2+ years they have known each other wearing matching clothing. 
What follows is usually a flood of questions wanting to know why they match, whose idea it was, and then they always want to know how on Earth I found so many outfits that match for the past two years.
I always tell them that "matching girls" was entirely my oldest's idea. When her sister was born in 2015, she wanted to make sure that everyone knew how excited she was about her baby sister and declared that they were going to match every day.