Though generally accepted as the most playfully entertaining form of popular media or art, animation as play has received little scholarly analysis. The author examines the nature of playfulness in animation and describes play as a critical tool in animation studies. Examining studio character animation from such perspectives as creative production, animated output, and audience reception, he builds on findings of animation studies, neuroscience, cognitive psychology, anthropology, semiotics, sociology, and aesthetics to propose a specific or ludic mode of animation. He then reviews how cinematic naturalism affects the nature of play in animation. He concludes that animation is a playground for the mind and that engagement with animated entertainment is authentic play. (Contains 2 figures.)