7. "What A Magnificent Head!"
The next exchange featured on this list is one from shortly after the Doctor and Solon meet. Naturally, in his quest to find the perfect head for Morbius, Solon would notice the magnificence of peoples' heads, especially the Doctor's...
Solon: Oh. What a magnificent head! Sarah: What? Solon: Superb head. The Doctor: Well, I'm glad you like it. I have had several. I used to have an old grey model before this. Some people liked it. Sarah: I did. Solon: What? The Doctor: I said, some people liked it, but I prefer this model.
The Doctor's proud tone in response to this remark is what makes for such joyful viewing. Fans of the show love when the Doctor makes light of his ability to regenerate, casually throwing it into conversation, and so this wonderfully matter-of-fact delivery makes for a moment of fan-service everybody can appreciate.