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) even though it is not mentioned by name. He suggested that the lack of a spark may be down to the fact that the Time Lords were no longer around to manage anomalies. In the 2006 episode "School Reunion", the Tenth Doctor and Sarah Jane Smith both seem to indicate in dialogue that they haven't seen each other since her departure from the TARDIS in "The Hand of Fear", although this contradicts their having met later during "The Five Doctors". In that story, she does not appear to realise that the Fifth Doctor is a later incarnation of the third