The Doctor (The Web of Caves)

A person calling himself "the Doctor" once landed on a planet where one of the inhabitants arranged with him beforehand exactly when and how he would attempt to take over the planet. (NOTDWU: The Web of Caves)

Behind the scenes

 * Mark Gatiss also portrayed an incarnation of the Master who appears in the Doctor Who Unbound story Sympathy for the Devil (although credited as "Sam Kisgart"). Along with Derek Jacobi, this makes Gatiss one of only two actors to have portrayed both the Master and the Doctor in licensed appearances.
 * Appearance-wise, this Doctor resembles the Eighth Doctor, who was the current Doctor at the time that the sketch The Web of Caves was broadcast.