A Boy's Best Friend
This story is set far in the future when habitation of the Moon has already taken place. Jimmy Anderson is a Moon-born ten-year old, and he owns a robotic dog named Robutt, whom he comes to love. However, his parents want him to have a real dog, a Scottish Terrier. Since Moon-borns cannot visit Earth, his parents bring the dog to the Moon. But since the relationship between Jimmy and Robutt is so close, Jimmy decides not to have the 'living' dog and keep the 'fake' dog Robutt instead.