Unlike a lot of paranormal phenomenon, myths and fantasies, Doppelgängers have only been around for just over two centuries, yet the name is firmly entrenched in the English language and western society. We often refer to people who share similar physical appearances as someone’s Doppelgängers.
Doppelgängers were the invention of Jean Paul, an eighteenth century German author, who put the two German words “doppel” (double) and “gänger” (goer, or walker) together, capitalized it as is often the case in German, and created a new mythical creature.
The Doppelgänger was an apparition that was the exact replica of the subject. The myth said that if a relative or friend saw the Doppelgänger, it meant the real person was in danger of illness or accident. If the subject saw his own Doppelgänger, it was very bad: it was considered a portent of coming death.
Doppelgängers don’t seem to be much more than a curiosity. They’re relatively harmless – they don’t do anything but scare the crap out of people. But what if they didn’t?
What if they were able to affect the material world in some way? Perhaps they, unlike the person they look like, don’t have the same moral code or social orientation. It could make an interesting story, don’t you think? How long before someone in that situation, when arrested, would point at their doppelganger and protest “it wasn’t me, it was the other guy!” and for the first time in fiction (or reality, probably) they would be speaking the truth.