The Doctor (Doctor Who)
Jodie Whittaker took over the role as the Thirteenth Doctor in the 2017 Christmas special. In addition to the above-listed actors, others have played versions of the Doctor for the duration of particular storylines.
Notably, John Hurt guest starred as the War Doctor in the closing moments of the 2013 episode "The Name of the Doctor", the webcast "The Night of the Doctor" and the 50th Anniversary episode "The Day of the Doctor". The War Doctor is an incarnation existing between those of McGann and Eccleston. Hurt was never the programme's lead actor; his Doctor was retroactively inserted into continuity for the programme's 50th anniversary, and was written so as not to disturb the ordinal naming of the established Ninth, Tenth and Eleventh Doctors. In the 1986 serial "The Trial of a Time Lord", Michael Jayston played the Valeyard, an amalgamation of the Doctor's darker sides from between his twelfth and final incarnations.
River Song (Doctor Who)
River Song is a fictional character created by Steven Moffat and played by Alex Kingston in the British science-fiction series "Doctor Who". River Song was introduced to the series as an experienced future companion of series protagonist the Doctor, an alien Time Lord who travels through time in his TARDIS. Because River Song is a time traveller herself, her adventures with the Doctor occur out of synchronisation; their first meeting (from the audience's perspective) is his first and apparently her last. While other actresses briefly portray younger versions of the character, Kingston plays her in 15 episodes, as River becomes a companion, romantic interest and eventual wife of the Doctor in his eleventh incarnation portrayed by Matt Smith.