The four doctors that J.D. helps, after being stuck with the needle filled with the Hepatitis A patient's blood, are all played by actors who starred in St. Elsewhere (1982), another show about young interns learning the ins and outs of the job. The actors are Ed Begley Jr., William Daniels, Stephen Furst and Eric Laneuville. Daniels played the chief of surgery Dr. Mark Craig, Begley and Furst played the residents Dr. Victor Ehrlich and Dr. Elliot Axelrod and Laneuville played the orderly turned physician's assistant Luther Hawkins. The four doctors all have a form of legionnaires disease, which was a major story arc in St. Elsewhere (1982)'s storyline.
This episode was part of NBC's 75th Anniversary celebration, in which actors from previous NBC shows guest starred in current ones.
When J.D. is signing on the Limited Liability form, you can see a face being drawn at the top right corner of the form.
Stephen Furst is well known for his role in Babylon 5, where the chief of medicine was a Dr Franklin. In this he plays Dr Franklyn.
William Daniels (Dr Douglas) also played a Doctor in Greys Anatomy. He played Dr Craig Thomas in several episodes of Series 9.