While there are many different versions of this, the most common one I've heard was that every person's birth coincides with two others in different parts of the world. All three grow to be exactly identical aside from certain personality traits. Basically one would get the brains, one the athletics, and the last the charm. If one should happen to die prematurely, those traits would then be transfered to the remaining two and if two of the doppelgangers should happen to make eye contact for whatever reason, they would die and the one remaining would essentially become one seriously amazing S.O.B.
Everyone can have a doppelganger.
You don't become a doppelganger, doppelganger exists by God.
I saw my doppelganger across the street, and it was like looking into a mirror.
Doppelganger Inc. is no longer existing.
It's because your doppelganger can pretend to be you or she might be standing right behind you when that person saw your doppelganger.
I would consider the antagonist as the creature he is. Not who he is but what he is, a Doppelganger.
Doppelganger - 1997 is rated/received certificates of: UK:PG
The cast of Doppelganger - 1979 includes: Donna Loney
Doppelganger - 2009 II is rated/received certificates of: USA:PG
It means that the doppelganger is coming after you or it's trying to tell you something.
You don't.
Doppelganger