SUSAN: The TARDIS can go anywhere.

BARBARA: TARDIS? I don’t understand you, Susan.

SUSAN: Well, I made up the name TARDIS from the initials, Time And Relative Dimension In Space. I thought you’d both understand when you saw the different dimensions inside from those outside.

IAN: Just let me get this straight. A thing that looks like a police box, standing in a junkyard, it can move anywhere in time and space?

SUSAN: Yes.

DOCTOR: Quite so.

IAN: But that’s ridiculous.