Kinetic energy is usually the entry point for the study of energy in physics and is often perceived as unproblematic. We present evidence, however, that some learners who seem to have accepted the concept, from elementary school students to college physics majors and in-service teachers, nevertheless do not consistently attribute kinetic energy to moving objects that are being pushed or carried by other objects. Factors that seem to contribute to this idea include that the passive object is not moving "on its own"; the lack of attributes, like wheels, that suggest the ability to move on its own; and the perception that it would stop immediately if the driving object were to stop or disappear. We interpret these observations in terms of a model of a conceptual change via assimilation rather than accommodation and suggest some possible instructional implications.