In retrospect, given that Stefan and Elena's romance was the driving force behind the genesis of The Vampire Diaries, it seems like vampires may not have deserved the headlining title. Because, clearly doppelgangers are one of if not the most important aspect of the series, at least in terms of pushing the narrative forward.
Doppelganger mythology is at the heart of TVD and is ultimately why so much of what happens to these characters actually happens. But despite the fact that doppelgangers were so essential to the series, there are many aspects of their story and mythology that really don't make sense.
Stefan And Damon Didn't Know About Tom Avery
On the one hand, obviously Damon and Stefan were not aware that Stefan was even a doppelganger, nor did they know what a doppelganger was until they ran into Elena.
However, they're vampires, they have nothing but time, and someone like Tom Avery cannot be very far removed from them given that 150-odd years is not that many generations. How is it that Stefan's twin was hiding out a few states away and they never knew?
Katherine Didn't Find Other Doppelgangers
What's even more difficult to understand is how exactly Katherine never found another doppelganger before Elena. Yes, Nadia was taken from her and she couldn't find her.
However, most people and bloodlines didn't venture too far from where they were born, and more importantly Katherine knew what to look for and finding a doppelganger for Klaus was life or death for her. If doppelgangers spring up as often as they seem to, why didn't Katherine find one before Elena?
Silas And Amara Didn't Appear To Have Children
The doppelgangers who are born are clearly all a part of the same bloodline, and it stands to reason that obviously the Silas doppelgangers would be his descendants and the Amara doppelgangers would be her descendants.
However, Silas and Amara both never mention having children, they're both quite young when they become immortal, and they both are unmarried. So where did the doppelganger line actually start?
Doppelganger Blood Is Like A Universal Cure-All
It's not entirely incomprehensible that doppelganger blood would be a powerful magical tool, but in a lot of ways it's hard to understand.
For all intents and purposes, doppelgangers are humans. It makes sense that something like the spell to make the Original vampires would use doppelganger blood, but it's odd that it seems to be an extraordinary mystical ingredient that bolsters the power of any magic or spell.
People Are Weirdly Obsessed With Them
That's not to say that Stefan, Elena, or even Katherine don't have their charms, but the fact that everyone who meets them seems to fall in love with them and have an almost delusional idealized view of them is strange.
Stefan is occasionally a gleeful serial killer, Elena can be a self absorbed monster, and Katherine would throw anyone under the bus to save her own skin, and yet everyone around them would still do anything for them.
The Doppelganger Bloodlines Never Intersect
According to the doppelganger mythology and Markos' spell that was designed to bring the doppelgangers together, doppelgangers of the original Silas and Amara have been finding each other and falling in love for centuries.
But if that were the case, then why exactly are they even two separate bloodlines? If human versions of the doppelgangers keep coming together and falling in love, why wouldn't at least one set of them marry and have children?
The Doppelgangers Are Difficult To Find
It's hard to tell how often doppelgangers are actually born. Initially it appeared that it's at the very most a 500 year interval, but Stefan's birth in the mid-1800's makes it seem like they're more likely born around every 150 years or so. But if that's the case, then why are they so difficult to find?
Granted, they'd have to be found by someone like Klaus who actually knows what their quarry looks like, but someone with supernatural abilities or just basic common sense would be able to follow the bloodline if they were really interested.
The Travelers Didn't Find Them
Interestingly, Markos and the rest of the Travelers are one of the few groups of people in the world who actually know what to look for.
But if they cast a spell to bring the doppelgangers together, and the doppelgangers do keep coming together, and they have a shot at finding them every century and a half or less, then why didn't they ever actually find them?
Doppelganger Destiny Doesn't Make Sense
So according to Markos, he created some sort of love spell to constantly bring the doppelgangers together. But what happens when one doppelganger meets the wrong doppelganger for them?
For instance, when Katherine met Stefan, there was presumably another Petrova doppelganger out there who was "meant" for Stefan. Why wasn't she still drawn to her doppelganger match? And the same goes for Tom Avery and Elena, even though Elena already found a doppelganger, why didn't Tom keep feeling the pull towards her?
There Aren't Any Mikaelson Doppelgangers
Perhaps the white oak was the only loophole that nature needed when it came to the Mikaelsons, but what's quite confusing is that if the doppelgangers exist because Amara and Silas are true immortals, and Esther essentially used the same spell to make the Mikaelsons into Originals, why aren't there any Mikaelson doppelgangers?
Clearly Silas and Amara weren't "true immortals" either because the cure existed, so why did they have doppelgangers and the Originals didn't?