Trivia: When Harriet Jones is explaining the sub-wave network to the Doctor's companions she says "It was created by the Mr. Copper Foundation." This is a reference to Mr. Copper from "Voyage of the Damned", who stayed to live on Earth and who probably would have had the advanced technology from the planet Stow where he came from.
Add timeProfessor Lazarus
Trivia: The Doctor mentioning that someone tried to move the Earth once before, a long time ago, is a reference to the First Doctor serial "The Dalek Invasion of Earth", in which the Daleks intended to replace the planet's core with an engine in order to do the moving. And, of course, the Daleks are responsible for this episode's titular planet theft as well.