What are babies?

I was holding the baby today. She is almost 13 months old and talking and walking all over the place. Lately she has been particularly cute, I was holding her while we were doing some schoolwork today and I asked, "What are babies? What are they? Babies are....?" I waited for one of the children to answer. After a few seconds Anna who is six answered, "Floor cleaners," a pause, "because they pick up everything they find that's on the floor."