On a more artistic note, The Stranger is a song from the album of the same name by talented American singer & songwriter, Billy Joel. It is about how we think we know somebody and then find out often harshly that were actually strangers to us.
Girl 1: So I found out my husband of 7 years has been having an affair with another man for the past 4.
Girl 2: The Stranger can be a real prick sometimes, huh?
Girl 1: I should have listened to Billy Joel...