This story was the first to use a new title sequence incorporating an image of Patrick Troughton's face, designed by Bernard Lodge and realised by Ben Palmer. The series' theme was also rearranged slightly at this point by Delia Derbyshire, with assistance from Dick Mills.
The Macra seen to be in charge in the final episode is white rather than black.
OTHER FORMATS:
The Second Doctor Novelisations
Audio Adaptions
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