Magnum P.I. second intro. (Video) 1 discussions This is the second intro to Magnum P.I. which was one of many iconic TV themes written by Mike Post. The theme made its debut during the mid-first season of the show, and even replaced the opening.. Tags: Magnum P.I. Rick T.C. Higgins Tom Selleck John Hillerman Roger E. Mosley Larry Manetti