The Doctor (Doctor Who) footage. Tom Baker did reappear, but as "the Curator", an ambiguously different character who he was not credited for playing. A voice actor, John Guilor, recorded a line of audio impersonating the First Doctor, for which he was credited as "Voice Over Artist". In other multi-Doctor stories, the multiple actors are all credited as "The Doctor", the exception being "The Three Doctors" (1972–73), which credited William Hartnell, Patrick Troughton and Jon Pertwee as "Doctor Who" as the 1972 serial preceded the practice of crediting the character as "The Doctor". In "Human Nature" (2007), the plot involves the Tenth Doctor altering
The Doctor (Doctor Who) that he had no intention of showing the regeneration in the series, and that he believed the story of how the Eighth Doctor became the Ninth is best told in other media. In "Doctor Who Confidential", Davies revealed his reasoning that, after such a long hiatus, a regeneration in the first episode would not just be confusing for new viewers but lack dramatic impact, as there would be no emotional investment in the character before he was replaced. The circumstances of the Eighth Doctor's regeneration were explored during the 2013 specials, with the revelation of the incarnation played by Hurt