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.
Philip Madoc
Madoc appeared in the second "Doctor Who" film, "Daleks' Invasion Earth 2150 A.D." (1966) and later in the BBC series itself. He appeared in two Second Doctor serials — "The Krotons" where he played Eelek, a high-ranking member of Gond Society, and "The War Games", where he played the villainous alien War Lord. In the 1970s he appeared in two Fourth Doctor serials — "The Brain of Morbius" and "The Power of Kroll". He recorded DVD commentaries for "The Krotons", "The War Games" and "The Brain of Morbius" and was interviewed about his roles in "Doctor Who" in the short film "Philip Madoc - a Villain for All Seasons", which appeared as an extra on the DVD for "The Power of Kroll". In 2003, he guest-starred in the "Big Finish" "Doctor Who" audio adventure, "Master", and returned to Big Finish in the 2008 Sixth Doctor story "Return of the Krotons". He voiced the War King in the "Faction Paradox" audio series.