William Hartnell (Jeff Richards) and Patrick Troughton (Tramp) would both later achieve widespread fame for playing the Doctor in Doctor Who (1963). Hartnell played the First Doctor from 1963 to 1966 while Troughton replaced him as the Second Doctor from 1966 to 1969. This is their only television appearance together outside of Doctor Who (1963), although they never physically share a shot in either.
William Hartnell, Patrick Troughton, Robert Beatty and Bill Fraser all later appeared in Doctor Who (1963), Hartnell and Troughton played the titular role, Beatty appeared with Both in The Tenth Planet which saw the first changing of the role, whilst Bill Fraser would appear in Meglos and later the first Spin off K-9 and Company: A Girl's Best Friend (1981).
A police recruitment poster can be seen outside the police station. It shows a depiction of Jack Warner in his role as Sgt. George Dixon from the TV series Dixon of Dock Green (1955).
Bill Fraser essentially replaced William Hartnell on The Army Game.