Second Doctor
The Second Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series "Doctor Who". He was portrayed by character actor Patrick Troughton.
David Langton
In 1968 director Douglas Camfield chose Langton to portray Colonel Lethbridge-Stewart in the "Doctor Who" serial "The Web of Fear", but Langton dropped out to perform in a TV play before production began, so Camfield gave the part to Nicholas Courtney, who had originally been cast in different role. As played by Courtney, the character of Lethbridge-Stewart (better known as the Brigadier) returned to "Doctor Who" the next year and became one of its most recognisable supporting characters, appearing in "Doctor Who" irregularly until 1989 and making a final appearance in spin-off "The Sarah Jane Adventures" in 2008.