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.
Peter Capaldi
Capaldi was cast in 2013 as the Doctor in the BBC science-fiction series "Doctor Who". His casting was announced on 4 August 2013 in a special BBC programme hosted by Zoë Ball. Capaldi first appeared as the Doctor in a cameo in the 50th anniversary special, "The Day of the Doctor", before appearing in the 2013 Christmas special, "The Time of the Doctor". A lifelong fan of the series, Capaldi had previously played Lobus Caecilius in the 2008 episode "The Fires of Pompeii" with the Tenth Doctor and his companion Donna Noble, as well as playing civil servant John Frobisher in the 2009 spin-off "".