During an interview for the PBS series "Pioneers of Television," Noah Wyle said that while filming some of Carter's Africa storyline in the Kalahari Desert, the real on-set medic passed out from the heat, and Wyle (who by that time had been filmed pretending to perform hundreds of simulated medical procedures for the television show) inserted a real I.V. and hooked the medic up to a real saline drip.
Frank, the desk clerk (Troy Evans), always talks about life on the "force" as a Chicago police officer. In the first episode, he had an appearance as a police officer who was shot and treated by the ER staff.
Goran Visnjic named his character after the writers could not develop an appropriately Croatian name. The character is named for Visnjic's nephew (Luka) and his best friend (Kovac).
Although mostly shot at "Warner Brothers" Burbank soundstages, the cast and crew usually would make at least two trips to Chicago each season to shoot realistic exterior scenes for several episodes, which include many familiar Chicago landmarks. These scenes are typically shot on early Sunday mornings to avoid disrupting traffic.
The character of Dr. John Carter was named after the protagonist in the classic "John Carter: Man from Mars" pulp science fiction stories. Michael Crichton, like many science fiction writers, considers it an early influence.