As humans, we gather a wide range of information about other people from watching them move. A network of parietal, premotor, and occipitotemporal regions within the human brain, termed the action observation network (AON), has been implicated in understanding others' actions by means of an automatic matching process that links observed and performed actions. Current views of the AON assume a matching process biased towards familiar actions; specifically, those performed by conspecifics and present in the observer's motor repertoire. In this study, we test how this network responds to form and motion cues when observing natural human motion compared to rigid robotic-like motion across two independent functional neuroimaging experiments. In Experiment 1, we report the surprising finding that premotor, parietal, occipitotemporal regions respond more robustly to rigid, robot-like motion than natural human motion. In Experiment 2, we replicate and extend this finding by demonstrating that the same pattern of results emerges whether the agent is a human or a robot, which suggests the preferential response to robot-like motion is independent of the agent's form. These data challenge previous ideas about AON function by demonstrating that the core nodes of this network can be flexibly engaged by novel, unfamiliar actions performed by both human and non-human agents. As such, these findings suggest that the AON is sensitive to a broader range of action features beyond those that are simply familiar.