In John Smith's book, "A Journal of Impossible Things", sketches of previous actors who have played the Doctor are shown, marking the first time that the 2005 series has explicitly depicted the Doctors from Doctor Who (1963) and Doctor Who: The Movie (1996). The actors depicted on screen were William Hartnell, Peter Davison, Colin Baker, Sylvester McCoy and Paul McGann. Images of the Journal that were published on the BBC website reveal that the other remaining Doctors, Tom Baker, Jon Pertwee, Patrick Troughton, Christopher Eccleston, and David Tennant himself, were also illustrated on the page.
John Smith gives the names of his parents as Sydney and Verity. This is a reference to Sydney Newman (creator of Doctor Who (1963)) and Verity Lambert (the show's first producer).
When Martha has returned to the TARDIS and is watching the video the Doctor made for her she fast forwards through a long section before reaching the Doctor's last point. There was no actual script for what David Tennant was saying in this section, as we see in the deleted scenes. Instead he lets loose a babble that covers not only the fact that he has to talk for a minute and a half, but he also tells us about The Housemartins and a gig of theirs he saw in 1990, before wrapping up with a string of random words and sounds.
The receptacle for The Doctor's identity was changed from a cricket ball to a pocket-watch, as this was something which could actually be opened.
John Smith's skill with the cricket ball is reminiscent of that of the Fifth Doctor, best shown in Black Orchid: Part One (1982)/Black Orchid: Part Two (1982) and Four to Doomsday: Part One (1982)/Four to Doomsday: Part Two (1982)/Four to Doomsday: Part Three (1982)/Four to Doomsday: Part Four (1982).