Doctor Who Season 10
TMDB
season number: 10
number of episodes: 26
IMDb: tt0562963
overview
William Hartnell returned in a cameo as the First Doctor and Patrick Troughton in a more substantial role as the Second Doctor in The Three Doctors. This story marked the end of the Doctor's exile on Earth, opening up the series to more off-world adventures and beginning a gradual reduction of UNIT-related stories.