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.
Jack Watling
His reputation as an effective and reliable television actor took root in the early 1960s. Between 1964–69 he was Don Henderson, the troubled conscience to tough businessman John Wilder (Patrick Wymark) in "The Plane Makers" and its sequel "The Power Game". Watling also appeared as Doc Saxon in the 1970s series "Pathfinders". He played Professor Edward Travers in the BBC science-fiction television series "Doctor Who" in the serials "The Abominable Snowmen" (1967) and "The Web of Fear" (1968), both of which also featuring his daughter Deborah Watling as the Second Doctor's companion Victoria Waterfield. He reprised the role decades later in the independent "Doctor Who" spin-off video "Downtime" (1995).