Imagine you're driving home late at night and pass up a car exactly like yours waiting at the corner for you to pass. No, it's not unusual if you have a new car, but if you have a very distinctive, very old car and know that there's very few of these junkers still on the road...it is unusual. To make it even weirder, the other car pulls out behind you, you see the lights in your rear view for only a second and then it's gone - gone when there's nowhere it could have possibly turned off at. And then only a second later when you look up at your rear view to check that the identical car really is gone, you see headlights again, but it's a white truck behind you instead. Are you crazy? Or did another version of yourself slip in to this universe and back out into it's own parallel dimension?