This paper presents an empirically tested theoretical framework to explain user engagement and end-user satisfaction with interactive agents. Such a framework is not only important from a scientific point of view; application designers may find a set of dos and don'ts that help them create more satisfying embodied agents in different task domains and social settings. From a multidisciplinary perspective, we have conducted a series of experiments to verify underlying mechanisms in the processes of interacting and engaging with embodied agents in various task domains. Our results show that the most commonly held views are not always tenable; sometimes other factors provide better explanations for liking an embodied agent or end-user satisfaction. For example, it is not realism but rather affordances and ethics that are key for understanding user responses, and a beautiful design is not always the most preferable. From our results, guidelines for designers and future research are reflected upon. © 2009 John Wiley & Sons, Ltd.