We have made a number of robot applications as children toys. The design principles behind these applications are based on different artificial intelligence techniques. One of our main principles is to go away from the traditional play scenario of two intelligent agents such as child and "intelligent" computer game to a physical reality of the second intelligent agent. Hence, the game consists of a child playing with a physical robot that can be manipulated to different performances. For instance, we constructed a physical model of the old, popular computer game Pacman, where the child is to navigate a semi-autonomous LEGO Mindstorms robot around in a labyrinth while avoiding two fully autonomous "ghost robots". In other cases, we extend the games to include three intelligent agents: child, robot, and computer game, and in some cases, we even have four intelligent agents to interplay: child, robot, computer, and "intelligent" room.