If one would start speaking about the dragon kings and black swans, many people would think that the one is talking about the fairy tales. But these terms are used then speaking about the events in the financial markets! Black swans are rare, but observable in the nature. Dragon kings are only observed in the fairy tales. So we would be amused if we would see the black swan with our own eyes, yet if we would see the dragon king we would be completely shocked. In nature these kinds of event are extremely rare and improbable, while in the financial markets we see these kind of events frequently enough. Below you can find a talk by Didier Sornette (taken from ted.com, some of the related info is available from blog.ted.com), who talks about these kind of events, their impact and possibilities to predict.
Interestingly enough, Lithuanian media has already written about Didier Sornette (e.g., delfi.lt).