What you call one red-headed, freckled person that looks exactly like another red-headed, freckled person that you know. These people are often mistaken for each other, and hilarity ensues. Everyone in Ireland has at least three of these.
Normal Friend: Hey man, you didn't wave at me when I saw you on the street!
Ginger Friend: I don't think that was me...You must have seen my doppelginger.