The field of mobile robotics offers a new medium for public entertainment and art. Mobile robots can move, react, and interact in the real world, generating behaviors that can be used as a new artistic medium quite different from sculptures, drawings or video. This new medium, like other technological media such as video or the Internet, requires considerable technical know-how to be exploited successfully. The successful design of a mobile robot demands a strong interdisciplinary and systems-oriented engineering process. The addition of artistic constraints adds a new dimension to the engineering problem and reinforces the need for a coherent approach to the design. This paper illustrates this interdisciplinary approach with six examples of robotic art and entertainment projects that demonstrate the methodological issues needed for this type of work. Several aspects of the projects are discussed, including the artistic effects on the public, the sometimes problematic interaction between artists and engineers, and details of the mechanical, electronic and behavioral designs as applied to entertainment.