In one of his always delightful essays, Stephen Jay Gould traced the "evolution" of Mickey Mouse from the time of his creation by Disney, in 1928, to the mouse we know today. The early Mickey was a bit of a rascal -- mischievous, occasionally cruel. And he looked more or less like a real adult mouse: small head in proportion to body, pointy nose compared to cranial vault, beady eyes, spindly legs. As time passed, Mickey's personality softened and his appearance changed. Head and cranial vault became enlarged, eyes grew to half the size of the face, limbs got pudgier. Gould elucidated the evolutionary principle behind Mickey's transformation: It is called neoteny, or progressive juvenilization.
Mickey became a national symbol, and Americans like their national symbols cute and cuddly. Mickey's chronological age did not change, but he developed babyish features. To explain these perhaps unconscious developments on the part of Disney's artists, Gould referred to the work of animal behaviorist Konrad Lorenz, who believed that juvenile facial and body features release "innate triggering mechanisms" for affection and nurturing in adult humans. The adaptive value of this response is obvious, since the nurturing of young is necessary for survival of the species. According to Lorenz, evolution has provided us with a caring response to juvenile features, a genetically-programmed reaction that apparently overflows onto other species.
If Lorenz is right, teddy bears, Andy Pandas, and the young rabbit in the grass just now outside my window are beneficiaries of our innate nurturing response to big eyes, round craniums, and pudgy limbs. Even Mickey Mouse evolved juvenile features in response to our evolved preference for all things cute and cuddly.