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.
Second Doctor comic stories
When the War Games aired on the BBC and there was an absence in Doctor Who episodes broadcast, TV Comic continued to print comics featuring the second doctor and tied this into the series with the story line of when the second doctor was captured by the Time Lords in the end of the War Games and was put on trial for meddling in the affairs of other races and was forced to regenerate, he escaped with the help of the CIA (Celestial Intervention Agency) and worked with them for a while, until he was forced to return to Earth, where furthermore he hid from the Time Lords, fighting monsters until they sent what appeared to be scarecrows working for the Time Lords to force the second doctor to regenerate into the third. This story line became known as the Doctor Who Season 6B.