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) and the junkyard in which they find him bears the sign "I.M. Foreman". When addressed by Ian with this name, the Doctor responds, "Eh? Doctor who? What's he talking about?" Later, when Ian realises that "Foreman" is not the Doctor's name, Ian asks Barbara, "Who is he? Doctor who?" In an ultimately unused idea from documents written at the programme's inception, Barbara and Ian would have subsequently referred to the Doctor as "Doctor Who", given their not knowing his name. Throughout both the classic and revived programme, a running joke is that when the Doctor is introduced as just the