Frazer Hines
Hines' "Doctor Who" debut came in 1966, when he was cast to play the part of Jamie McCrimmon, the companion of the Second Doctor (played by Patrick Troughton). Originally intended as a one-off guest character, Jamie joined the regular cast and appeared in the series from 1966 to 1969. Hines reprised the role in a cameo in the 20th anniversary serial "The Five Doctors" (1983) and as a guest star in "The Two Doctors" (1985). Hines would appear in 117 episodes of "Doctor Who" in all—more than any other "companion" actor in the history of the series. The only actors appearing in more episodes are those who played the first four Doctors. Many of the episodes featuring Jamie no longer exist in the BBC's collection.
Fourth Doctor
The Fourth Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series "Doctor Who". He was portrayed by Tom Baker for seven consecutive seasons, which remains the longest tenure of any actor to portray the lead, counting both the classic and modern series. He was considered to be the most recognisable and iconic incarnation of the Doctor both in the United Kingdom and internationally.