RoboX is a tour guide robot, designed to interact with visitors at Expo02, the Swiss National Exhibition. During five months, ten RoboXs will be in contact with people not trained to autonomous robots and will guide them throughout an exhibition about robotics. The work exposed here was dedicated to make RoboX lifelike and credible in implementing an expression generator. This generator uses the robot capacities in order to best express its internal state which is influenced by its sensor entries and the scenario of the guided tour. In order to validate our approach, a short experiment was set up in order to present results that include appreciations of people not used to robots.