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) of the World" (2005). Writer and "Doctor Who" executive producer Steven Moffat has gone further, arguing that "a television series which embraces both the ideas of parallel universes and the concept of changing time can't have a continuity error – it's impossible for "Doctor Who" to get it wrong, because we can just say 'he changed time' ". Some of the stories during the Seventh Doctor's tenure, part of the so-called "Cartmel Masterplan", were intended to deal with this issue by suggesting that much of what was believed about the Doctor was wrong and that he was a far more