The relationship between Pearl Mackie and Peter Capaldi, and Bill and the Doctor as well, is fascinating and very different from the previous companion relationships, at least for this new series.
Because we have the Peter Capaldi doctor, [it's] a relationship between a much older man and a much younger girl.
Educating Rita -- the old film and play Educating Rita -- I thought was kind of a good starting point for that kind of relationship.
When you meet somebody who really does become incredibly close to you and it has an awful lot of what a romance has, except it doesn't have any sex or romance in it.
When you meet the people in your life who do become your great teachers, you do have a different sort of crush on them.
If the Doctor is teaching Bill, at a certain point teachers have to let their students graduate.
[...] people walk into the TARDIS for the first time and of course they know what to do if they go on the inside.
How the hell would you know unless you know that that little room with no chairs in it and a work station in the middle was a space ship?
There's so many things that we've accepted over the years that there is no rational reason to accept any of these things, including the the fact -- there's kind of a statement of intent at the end of the very first scene Bill's in, where she says, "Doctor what?" instead of "Doctor who?" because that's actually the more common expression.