Future robots need a transparent interface that regular people can interpret, such as an emotional human-like face. Moreover, such robots must exhibit behaviors that are perceived believable and life-like. In this work we will propose the use of fuzzy logic for effectively constructing the whole behavior system of these robots. This will not only simplify the design task, but also enrich human-robot interaction. The latter claim is justified by effortlessly generating intermediate and blend of emotions from a few basic emotions. Additionally, fuzzy motor commands yield smooth life-like motions and therefore improve believability.