Dr. Lucas McClaren was a psychiatric counselor.
When the Starbug crew were arrested by the revived crew of Red Dwarf, Dr. McClaren was called in to provide a psychological assessment of Kryten. He was a relentlessly cheerful and positive person, even under extreme pressure. The two of them sat down in a small office, where McClaren tried to be understanding and open while Kryten explained how he had come to be there.
As Kryten expanded on the fact that McClaren had died millennia before and been resurrected by the nanobots, the counselor became increasingly concerned for Kryten's sanity. He asked Kryten several times to check that his chair was firmly screwed down. When Kryten described his new emotions, his "mindless violence" program caused him to hit Dr. McClaren on the hand. McClaren was very interested to hear that it was Lister that had encouraged Kryten to break his programming. He then made the recommendation that Kryten be returned to his original factory settings. (RD: Back in the Red I)
When Kryten was given the choice of whether or not to accept the treatment, he found it difficult to imagine saying "No" to McClaren and his colleagues. Kochanski had suggested trying to picture them on the lavatory, but Kryten's imagination wasn't up to the task. Instead, he held the officers at gunpoint and made them sit on a nearby stall of lavatories with their trousers down. McClaren was embarrassed because he was wearing a pair of white stockings and suspenders under his uniform. (RD: Back in the Red II)
McClaren, like the rest of the reconstituted crew, has not been seen again since Season VIII.