The episode played on public expectations, as David Tennant's successor to The Doctor was soon to be announced. This was heightened by the fact that David Morrissey had apparently been in talks to play the Eleventh Doctor.
The set for the cyberfactory is actually the Torchwood Hub set from Torchwood (2006) cleverly disguised.
A notable edit was the elimination of a sequence on the staircase at Reverend Fairchild's house, in which the Doctor used a stethoscope to establish that the Other Doctor had just one heart. It was now felt that too much suspense would be squandered if it was revealed so early that the Other Doctor was human.
This was the first episode to be broadcast after David Tennant's announcement that he would leave the role of the Doctor in 2010. However, it is the last episode to be filmed and produced before the announcement, as Tennant was playing Hamlet for the latter half of 2008 and early 2009; in fact, Tennant announced his departure at a live broadcast during the 2008 National Television Awards during the intermission of that night's production, in full costume and flanked by two Danish guards.