Creative joint activity is a form of real-time dynamic problem solving in which people collaborate to reach a common creative goal (e.g., to solve a mathematical problem, to improvise a piece of music, to write a novel, to sketch a story, and so on). While there exist interfaces able to produce social, emotional, communicative signals while collaborating with single human users to go through the creative process, the design of embodied interfaces able to observe and simultaneously effectively support creative joint activity with multiple human users is still an emerging research field. We define Creative Embodied Interfaces (CEIs) such interfaces, having either anthropomorphic or non-anthropomorphic aspect, and being either physically or virtually present in the real world. We argue that CEIs will enable a novel interaction paradigm that could be exploited in several elds such as science, education, health-care, arts, entertainment, social inclusion, companionship. This article is aimed at providing definition and a first framework of CEIs combining psychological theories of creativity and computational models of social signal analysis/synthesis in avatars.