Several elements from this episode have been recycled throughout the years: * Two elements were recycled in TV: Logopolis: * The Master being the Doctor's dark half was alluded when the Fourth Doctor implied this to Adric and Nyssa. * The Master causing the Doctor to regenerate occurs when the Master's Anthony Ainley incarnation caused the Fourth Doctor to regenerate. * Their possible fraternal relationship was teased in TV: Planet of Fire by the Master's Ainley incarnation to the Fifth Doctor and Peri Brown (but TV: The Sound of Drums later dismissed this theory after the Tenth Doctor was asked this question by Martha Jones). * The idea of a corporeal 'dark side' was used in TV: The Trial of a Time Lord, when the Master's Ainley incarnation revealed that the Sixth Doct