First Doctor: What have you done to it?

Twelfth Doctor: Nothing.

First Doctor: The windows… they’re the wrong size! The colour… I’m sure it’s changed! Look at it. It seems to have… expanded!

Twelfth Doctor: Well, it’s all those years of bigger on the inside – you try sucking your tummy in that long.

From Doctor Who – Season 11 Episode 0: ‘Twice Upon a Time’ (11×00 / Christmas special 2017)