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.
Eighth Doctor
The character was introduced in the 1996 TV film "Doctor Who", a back-door pilot produced in an unsuccessful attempt to relaunch the series following its 1989 cancellation. While the Eighth Doctor initially had only one on-screen appearance, his adventures were portrayed extensively in subsequent spin-off media, including more than 70 audio dramas starring McGann. In 2013, the actor reprised the role in the mini-episode "The Night of the Doctor", which depicts the Eighth Doctor's final adventure and his regeneration into the War Doctor (played by John Hurt).