Thomas Sullivan Magnum IV (Tom Selleck) was a Vietnam War veteran. At the time, Vietnam and its aftermath were still controversial. Magnum, Theodore "T.C." Calvin (Roger E. Mosley), and Orville "Rick" Wright (Larry Manetti) have been cited as some of the first positive portrayals of Vietnam veterans on a network television series.
A few episodes, particularly in season four, focused mainly on one or more secondary characters, due to Tom Selleck's movie shooting schedule, he was sometimes unavailable to film full episodes.
Magnum's Navy uniform includes the blue and white ribbon for the Navy Cross and the Naval Special Warfare insignia. That means he was a S.E.A.L., and earned the nation's second-highest award for Naval personnel.
In an interview for "Bravo TV's Countdown of the 100 Greatest Television Characters" Tom Selleck said his character, Thomas Sullivan Magnum IV, was initially written as a "James Bond of television, visiting stewardess on each arm, flawlessly perfect" kind of character, which Selleck hated. By his own admission, he told the writers and producers "I'm tired of playing what I look like." When asked what he wanted to do, Selleck remembered how much fun he had working with James Garner on The Rockford Files (1974) and suggested making Magnum more of a laid back, blue collar average Joe. His rationale was that if men watched the show and were able to identify with him, it would bring in even more male viewers. The writers and producers initially refused, and Selleck threatened to do Raiders of the Lost Ark (1981) instead. The writers and producers relented and Magnum became the approachable, charming jock character for which Selleck would become famous.
This is one of a very small number of shows in which an actor "breaks the fourth wall" and looks right into the camera. Thomas Magnum does this on occasion when presented with a ridiculous situation.