Headaches, three headed watch dogs, and the evolution of such.
According to Greek mythology, the three-headed watchdog Cerberus was said to guard the entrance to Hades. Although it was sometimes said to have as many as a hundred heads, most accounts describe Cerberus as having only three heads and the tail of a serpent. The center head was that of a lion, and the other two resembled a dog and a wolf. Cerberus was the offspring of the giant Typhon and Echidna, a monstrous snakelike creature. Heracles temporarily brought Cerberus to the upper world as the last of his Twelve Labors.