Doppelganger: (German) the ghostly double of a living person; has come to refer to any double or look-alike of a person; one's living "twin."
Came across a picture of a pianist/singer named Sarah Bareilles on a friend's blog the other day. Here she is:
Which blew my mind a little bit. Wanna know why? Because I went to high school with a girl who was also a pianist/singer, named Sarah Hayes (now Plankenhorn). Here she is:
Not the same person.
Did your mind just explode a little bit? Yeah, the world is a weird place.