For instance, on the planet 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 - whilst 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.

So long, and thanks for all the fish. Final message from the Dolphins, as they escape just prior to Earth's destruction.

Curiously enough, the dolphins had long known of the impending destruction of the planet Earth and had made many attempts to alert mankind of the danger; but most of their communications were misinterpreted as amusing attempts to punch footballs or whistle for tidbits, so they eventually gave up and left the Earth by their own means shortly before the Vogons arrived.