Autonomous technology is becoming more prevalent in our daily lives. We investigated how children perceive this technology by studying how 26 participants (3-10 years old) interact with Amazon Alexa, Google Home, Cozmo, and Julie Chatbot. We refer to them as "agents" in the context of this paper. After playing with the agents, children answered questions about trust, intelligence, social entity, personality, and engagement. We identify four themes in child-agent interaction: perceived intelligence, identity attribution, playfulness, and understanding. Our findings show how different modalities of interaction may change the way children perceive their intelligence in comparison to the agents’. We also propose a series of design considerations for future child-agent interaction around voice and prosody, interactive engagement, and facilitating understanding.