Surgeon (The End of the World)

The Surgeons were two people of unknown origin and race.

Their white suits covered their bodies and faces. They looked human but were not, given that Lady Cassandra O'Brien was the last human at that time. They worked for Cassandra by spraying her with water to keep her alive.

They appeared to be just employees of hers, until she threatened the Ninth Doctor that they would spray him with acid. When Cassandra teleported away, the surgeons came with her, but when the Doctor teleported her back, they did not return from wherever they had gone. (DW: The End of the World)