Surgeon (The End of the World)

Two humanoid surgeons worked for Lady Cassandra, spraying her with moisture to keep her alive. Their white suits covered their bodies and faces.

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 went with her, but when the Doctor teleported her back, they did not return from wherever they had gone. (TV: The End of the World)