Dallis claimed he created the strip to inform the general public about medical issues in an entertaining manner. For instance, a continuity from 1970 depicted the plight of an attractive young woman who frequently experienced gaps of "missing time": Morgan diagnosed her as suffering from "petit mal". In later years, the story plots moved away from medical themes as Rex and June alternated in stories, confronting threats and danger from a variety of malfeasants. A popular story took place in 2006, in which longtime character Dr. Troy Gainer was revealed to be a fraud. Beginning in 2016, artist-writer Terry Beatty often put Rex back in medical settings, either at his clinic or in the hospital. Beatty also had Morgan tackle pseudoscience in the form of a scam perpetrated by a recurring con artist character, as discussed in a 2019 interview in Skeptical Inquirer.