Copycat is a computer model of analogy-making in the domain of letter-string puzzles. Given an analogy problem such as “abc ⇒ abd; iijjkk ⇒?”, for example, it comes up with a set of various answers such as iijjll, iijjdd, iijjkl, iijjkd, iijjkk, iikjkk, iidjkk, or even abd or aabbdd.

Puzzles such as these are common in aptitude tests because apparently they provide useful measures of people's intelligence and creativity. Copycat, by the same token, is believed to have some degree of creativity, albeit a minute one. This model, its successor Metacat, and its siblings Letter Spirit, Tabletop, Phaeaco, and others owe their original conception to Douglas Hofstadter and his Fluid Analogies Research Group. Hofstadter believes that analogies are at the core of human cognition and creativity, and that computer models of analogy-making can provide useful insights into the mechanisms underlying the marvels of human intelligence, from art to science and from language to music. In this chapter, we study a few models of creativity and analogy-making, in particular Copycat, which is based on Hofstadter's views.