Do you remember that oddball week during the school year when everybody was supposed to show their school spirit by dressing in certain ways? Let's see -- there was "crazy hair" day, then "wild socks" day, then "dress like twins" day and so on.
What is it that so attracts us to be a twin with someone, even if we're only dressing like one another for one day? Is it that deep longing for connection? Is it symbolic of our desire to be understood as we understand ourselves? Is it an archetype for Twin Souls? Perhaps so.
In any case, it beats "crazy hair" day by a long shot.