The role that Cleavon Little played, Dr. Jerry Noland, was not originally written for a black actor. Frankie Avalon and John Rubinstein were among the actors considered for the role. (The beach movies that Avalon had appeared in with Annette Funicello were directed by William Asher, the producer and occasional director of "Temperatures Rising".) However, Asher's wife, Elizabeth Montgomery, spotted Little doing a guest appearance in an episode of All in the Family (1971), and then recommended him to her husband. Likewise, Montgomery also recommended Nancy Fox to Asher after spotting Fox in a toothpaste commercial.

At the end of the first season, the kindly doctor with the gentle sense of humor played by James Whitmore, was replace by an uptight administrator with a mother complex played by Paul Lynde.

The third and final format of the series aired as a summer replacement series in the summer of 1974. Paul Lynde and Cleavon Little were retained from the second season while all the supporting characters were dropped. Alice Ghostley, who had made a guest appearance in the first season, became a series regular as the hospital's head nurse who was also Paul Lynde's sister. Playing other nurses were Barbara Rucker and Nancy Fox, the latter returning from the original cast. William Asher was also brought back as producer.

The second season of the series was produced by Duke Vincent and Bruce Johnson and featured a "black comedy" approach similar to the film The Hospital (1971) starring George C. Scott. Paul Lynde played the new penny-pinching chief-of-staff, with Sudie Bond as his mother, the owner as well as a patient at the hospital. Barbara Cason was the hospital administrator, Jennifer Darling played a nurse, and John Dehner and Jeff Morrow alternated as pompous surgeons. Cleavon Little was the only actor retained from the original cast. Due to poor ratings the series was placed on hiatus after only 13 episodes of the second season.

The first season of this series was produced by William Asher and starred Cleavon Little as the jive-talking intern whose outlandish but well meant shenanigans outraged the hospital's chief-of-staff, played by James Whitmore. Joan Van Ark, Reva Rose, and Nancy Fox played the nurses who were always in cahoots with Little. Whitmore referred to Little and the nurses as "The Four Horsemen of Aggravation."

Sheldon Keller, the author of the series' original pilot episode, based it upon "This is a Hospital?", an unsold and unaired pilot that he wrote in 1965. This pilot, which was also produced by William Asher, starred Shecky Greene.

For her screen test, Nancy Fox acted with Anita Gillette. Fox won the part while Gilette's role was given to Joan Van Ark.