Per the title, D.H.Q. stands for 'Divisional Headquarters'.
Friday and Gannon discussed that they'd been working the hospital detail together for "three years - thirty-six months".
Sydney Soule plays the role of a Receptionist in this episode. She is the daughter of actor, Olan Soule, who also appears in this same story, as a Doctor.
Sergeant Friday (Jack Webb), talking with a patient of the gains made in mental health treatment, shows him a copy of the California Mental Health Act and assures him it is a good program, stating it was even signed by the Governor. At the time this episode aired, the Governor of California was Ronald Reagan, who served as the 33rd governor of California from 1967-1975. Ronald Reagan went on to become the 40th president of the United States, serving as president from 1981 to 1989.