A topic on dolphin intelligence naturally led to this, and derailed the topic. So I'm moving stuff.
It's an important and popular fact that things are not always what they seem. For instance, on the planet Earth, man had always assumed that he was the most intelligent species occupying the planet, instead of the third most intelligent. The second most intelligent creatures were, of course, Dolphins, who, curiously enough, had long known of the impending destruction of Earth.
Man had always assumed that he was more intelligent than dolphins because he had achieved so much–the wheel, New York, wars and so on--while all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man--for precisely the same reasons.
The dolphins made many attempts to alert mankind to the danger, but their communications were misinterpreted as amusing attempts to punch footballs or whistle for tidbits.
The last ever dolphin message, in fact, was misinterpreted as a surprisingly sophisticated attempt to do a double backwards somersault through a hoop while whistling The Star-Spangled Banner, but in fact the message was this: "So long, and thanks for all the fish."
After saying this, they promptly escaped the planet by their own methods. Eventually, they set up a "Save the Humans" campaign and rebuilt Earth exactly as it was minutes before the Vogons destroyed it, but that's in an entirely different book in the series.
Hitchiker's Guide to the Galaxy. Discuss it and all of 42.