Doppelgängers, evil or otherwise, are an interesting concept. How many times, for instance, have you heard someone you just met, gush something along the lines of: "You remind me so much of my friend such-and-such!" or "You look exactly like this girl I used to know in Anchorage!"? Yet you never get to meet these people, who are supposedly so very much like you. Ever wonder why? I do. I'm an only child, so I've always been fascinated by the idea that there could be someone out there, who might bear my likeness, who might talk the way I do, or dress like me, with whom I might share a certain identical gesture, or mannerism. That they might be a total stranger, makes this thought all the more thrilling.
There's a reason, however, why you're never suppose to meet your non-biological twin. In mythology Doppelgängers are often seen as harbingers of death, or other calamities. They are, in a way the ghost of you, before you're dead, or an evil self trying to take over your life. Seeing one usually forewarns you of your own demise. The poet Shelley, for instance, was reported to have met his, shortly before his death. It is said that these doubles cast no shadow, and sometimes can't be seen by others, though Shelley's likeness was supposedly seen by his landlady and one of his friends too.
Be that is it may, the next time someone tells me they know a person who looks exactly like me, I'll demand evidence and perhaps, if I dare, an introduction.
(they're not related as far as I know...)