Captain (The Curse of the Black Spot)

The Eleventh Doctor once discovered an unnamed individual who had apparently died on board an unnamed ship that crashed on the Fancy in the 17th century, in another dimension. This crew member, along with the rest of the crew, caught a human disease and died. The virtual medic on board had no patients to care for, so it took a human form and started taking pirates. (TV: The Curse of the Black Spot).

Behind the scenes

 * Although not named in the episode, the alien's shoulder had the abbreviation D.I.H.S. on it, which may be of some relation to either the unnamed ship or the species.
 * The Doctor Who Encyclopedia names this species as the 'Skerth', although this is not canonical.