Social worker

Upon meeting the Sixth Doctor and Peri, Olivia Jennings thought that they were social workers. (AUDIO: The Curious Incident of the Doctor in the Night-Time)

When the Eleventh Doctor showed up at Alex's door, he assumed that the Doctor was a professional from Social Services, as he knew Claire had phoned them. Alex realised that he wasn't a social worker after the Doctor told him that George's monsters were real. (TV: Night Terrors)

Two skinheads assumed that Lady Peinforte and Richard Maynard were social workers, even after they stripped the skinheads of all their clothes, and tied them upside-down from a tree. (TV: Silver Nemesis)

Behind the scenes
Neil Penswick, who wrote the NA novel The Pit, was also a specialised social worker by profession.