The Doctor says, "It shouldn't take that long to reverse the polarity. I must be out of practice". "Reverse the polarity!" was the catchphrase (and strategy) of Jon Pertwee's Third incarnation of Doctor Who (1963) in the early 1970s.
The set piece for the capsule of Lazarus's Genetic Manipulation Device is actually the redecorated descent capsule from The Impossible Planet (2006)/The Satan Pit (2006).
A scene cut from the episode, but included as an extra with the DVD release, reveals that the Doctor participated in the writing of the Declaration of Independence and in fact carries a copy of the first draft folded up in the pocket of his dinner jacket. An outtake of this scene is featured on the DVD as well, in which the Doctor has completely unfolded the document, only for David Tennant to realise that he and Freema Agyeman have run out of track.
An old head-cast of Vincent Price was tracked down and used by Neill Gorton to add an aged and wrinkled look to the prosthetics Mark Gatiss wore when playing the elderly Dr Lazarus.
Several of Stephen Greenhorn's initial ideas had to be discarded because they were too similar to concepts being developed either for the first season of Torchwood (2006) or (in the case of using the Thames Flood Barrier as a setting), The Runaway Bride (2006).