This series takes place in the TARDIS asks the question "what does the doctor do when his companions are asleep"?
Did You Know?
The director, Richard Senior, states that they're showing a TARDIS materializing inside of a Tardis and that in 40 Years of Doctor Who it's never been done, so he feels he's making "history". Actually, it's been done at least two other times: in the Jon Pertwee Adventure, "The Time Monster", where the Doctor and the Master materialize their tardises several times inside each others. It was probably best done in "Logopolus", a Tom Baker episode when the Tardis materializes multiple times inside itself. See more