It's 1913 in England, and an ordinary schoolteacher called John Smith
is disturbed by dreams of adventures in time and space and a mysterious
blue box. But, when lights in the sky herald the arrival of something
strange and terrible, Smith's maid, Martha
, has to convince him that he alone can save the world.
- John Smith's journal features sketches of the interior of the TARDIS, a sonic screwdriver, K9, Rose Tyler, Autons, Clockwork Droids, Cybermen, Daleks, the Moxx of Balhoon and Raxacoricofallapatorians as well as a picture of the gas-mask plague carriers from "The Empty Child"/"The Doctor Dances". Also the First, Fifth, Sixth, Seventh, and Eighth Doctors appear, the first time in the new series that the previous incarnations have been explicitly acknowledged on-screen..
- As part of his cover story, John Smith refers to his parents Sydney and Verity, a reference to one of the creators and the first producer of Doctor Who respectively. Russell T. Davies confirmed this in Doctor Who Confidential.
- Fleeting clips of the lone Dalek in "Dalek", Cybermen, Ood, Sycorax, the werewolf seen in "Tooth and Claw", Racnoss and Lazarus in his mutated form are shown when Timothy opens the watch. There is also a clip of the Doctor using his sonic screwdriver in "Army of Ghosts" and "The Age of Steel".
- John Smith's skill with the cricket ball is reminiscent of that of the Fifth Doctor, best exemplified in Black Orchid.
- In the flashback the Doctor mentions a Time Agent vortex manipulator.
- The melody used while Lucy is walking down the path is similar to the melody used in Remembrance of the Daleks when the Girl appears.
- The Family's possession of Lucy Cartwright is a nod to the
character of Aphasia in the original novel, a shapeshifting Aubertide
who likewise takes the form of a young girl with a balloon.
- The Doctor explains he will cloak the pocket watch with a "perception filter". The Torchwood episode "Everything Changes" coined the phrase when stating that some of the TARDIS's properties became welded to Roald Dahl Plass due to the activities of the Cardiff Rift. In Torchwood, the perception filter cloaks the Torchwood Hub's lift from the untrained eye.