Animal live streaming (i.e., live streams that feature animals) has recently gained popularity. Nevertheless, little is known about the effect of leveraging viewer-animal interaction on the live streaming experience. In this regard, we introduce MeowPlayLive, a live streaming system that allows viewers to interact with the cat in the live stream by sending voice messages. Since messages appear as moving objects on a tablet screen perceivable by the cat, viewers can win a chance to get heard when the cat decides to tap on the objects. By deploying MeowPlayLive in actual live streams, we found that voice message-based viewer-animal interaction motivates viewers to become active participants, renders the live stream more enjoyable, enhances viewers' attachment to the cat, and positively transforms the streamer-cat relationship. Our results suggest that viewer-animal interaction should be animal-driven, collaborative, and rewarding. We hope to inspire researchers to explore new forms of technology-mediated human-animal interaction.