Robots designed to co-exist with humans in domestic and public environments should be capable of interacting with people in an enjoyable fashion in order to be socially accepted. In this research, we seek to set up a small humanoid robot with the capability to provide enjoyment to people who pick up the robot and play with it by hugging, shaking and moving the robot in various ways. Inertial sensors inside a robot can capture how its body is moved when people perform such “full-body gestures”. Unclear is how a robot can recognize what people do during play, and how such knowledge can be used to provide enjoyment. People’s behavior is complex, and naïve designs for a robot’s behavior based only on intuitive knowledge from previous designs may lead to failed interactions. To solve these problems, we model people’s behavior using typical full-body gestures observed in free interaction trials, and devise an interaction design based on avoiding typical failures observed in play sessions with a naïve version of our robot. The interaction design is completed by investigating how a robot can provide “reward” and itself suggest ways to play during an interaction. We then verify experimentally that our design can be used to provide enjoyment during a playful interaction. By describing the process of how a small humanoid robot can be designed to provide enjoyment, we seek to move one step closer to realizing companion robots which can be successfully integrated into human society.