Amy: So, uh, what about dinner?
Sheldon: Is it me or are you purposely changing the subject?
Amy: No. And on the subject of subjects, is your use of the word "subject" the same or different as when we speak about the subject of a king?
Sheldon: I have a feeling you're still doing it. But I find that topic irresistible, so, now, in ancient Mesopotamia, the king referred to the people as his property.