Berk's Forumvine

See, there's a lot of references to things which happen in the future, especially by the Twins. Stockholm Syndrome, Penicillin, diving bells, air resistance, plasma, emergency rooms, ice cream, radio shows, rhetorical questions (rhetoric not being recognized as a literary device by that culture at that time), allergies, Shakespeare references, and soooooooooooooooooo many other things. Essentially, there is no way they should know most of that stuff. Additionally, there are several points where their culture is totally wrong. For instance, Vikings didn't actually have horned helmets, except perhaps for ceremonies. They didn't call themselves Vikings, either -- they just called themselves by their tribe names.

Now, you can look at all these things as comic relief and/or oversight by the writers.
But what's the fun in that?
What if... HTTYD happens not in the past, but in the future?
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Imagine a world which was disjointed and torn by war. An alien species releases some dragons on it to take advantage of its weakened state. The dragons, which were mistreated by the aliens, fight ferociously, raiding people and breaking technology. But instead of being conquered, the world instead splits back into different countries than before. These new countries all stopped the fighting and concentrated on keeping the dragon population low. Although they succeeded in not being overrun, most modern technology and knowledge was lost to most people.

One of those countries, in Scandinavia, was formed after the traditions of the Ancient Vikings. It even called itself the Viking Union, and took on many of the pop culture notions of Vikings, such as the horned helmets and the runic written language. After a long time, that Viking Union split up, and certain tribes formed -- such as the Hooligans, or the Berserker tribe, named after the ancient tribe of the same name.

In the meantime, the dragons, though they continued to be a nuisance, slowly lost most of their ferociousness.

However, some knowledge remained. The Thorston Clan passed knowledge down from parent to child, writing and recording the information. That's how the Twins know so much more than everyone else -- they keep dropping hints about the things they know. (e.g., "I had a cousin in Stockholm that that happened to once.") But they don't want to come right out and say it because someone might use the knowledge for wrong purposes. It helps that nobody believe them because they're... well... the Twins.

Of course, some things just stayed common knowledge, such as the existence of plasma. That's how other Vikings than just the Twins seem to know things that Vikings just didn't know.

Is it a good theory? Maybe. It's good enough that I'm writing a fanfic with it at the center.