Small moments that make you smile?

The scene in Timelash where Herbert comes out of his hiding place in the TARDIS and casually trades greetings with an absent-minded Doctor. I always chuckle at that bit especially when Baker realizes that Herbert shouldn't be there.

"Psst.. the TARDIS is a type 40."

Doctor: I don't suppose you've completely ignored my instructions and secretly prepared any Nitro Nine, have you?
Ace: What if I had?
Doctor: Naturally you wouldn't do anything so insanely dangerous as to carry it around with you, would you?
Ace: Of course not. I'm a good girl. I do what I'm told.
Doctor: Excellent. Blow up that vehicle.

''I can see why they made you librarian!''

"Morbius was executed for leading the rebellion. His body was placed in a dispersal chamber and atomised to the nine corners of the universe."

That one line in Morbius "the nine corners of the universe."

The sisterhood of Karn was one of the more strange and alien groups we ever get to meet in Doctor Who. It doesn't make any damn sense at all, but the whole idea of how strange they are is conatined within in that one line: It shows that the sisterhood of Karn know something about the universe that we have yet to even concieve of. And the way Ohica deilvers the line I don't doubt that the universe has 9 corners for a second.

They're thousands of years old, have been repeating the same rituals over and over for literally millennia, know nothing of technology (are confused by the Doctor's matches at the end), yet have been psychically probing the universe for so long they understand things about space and time of which mankind has yet to even guess at. Even the Time Lords formed an alliance with them; to the Time Lords other species are for the most part just too primitive to bother with, they wouldn't interact with them as equals unless they thought their mental powers quite serious.

I think the sisterhood were one of the most interesting creations in Doctor Who. I wish they had revisited them at some point. This is why I like Doctor Who: it is a window into strange and unusual worlds that make you think about things in new ways, question the nature of reality. I wish we still had writers like Terrance Dicks and Robert Holmes.