Mark Harmon returns to 'NCIS' for a special crossover with 'NCIS: Origins,' airing Tuesday at 9 p.m. ET/PT on CBS. | Entertainment Tonight

**NCIS** has become one of the most successful and enduring television dramas in history, captivating audiences for over two decades. The series follows a team of special agents from the Naval Criminal Investigative Service as they solve complex crimes involving the U.S. Navy and Marine Corps. From its very first episode, *NCIS* established a unique blend of action, humor, and heartfelt storytelling that set it apart from other procedural dramas. The characters’ strong chemistry and emotional de