TMDb/NCIS Celebrity Mark Harmon reflects on NCIS's evolution and a major character death in its 500th episode. Explore the show's new era without Gibbs. April 5, 2026 AceShowbiz - Mark Harmon expressed strong feelings about a significant character death on NCIS, the CBS procedural that debuted in 2003 and has become a staple of network television. After more than two decades of portraying Leroy Jethro Gibbs, Harmon witnessed the series transition into a new era following Gibbs' retirement in season 19.