Mark Harmon played special agent Leroy Jethro Gibbs for 18 seasons of NCIS before leaving in Season 19. The original show has soldiered on without him — it will soon be back for its 24th season — but the franchise has had trouble letting him go. Harmon showed up as Gibbs in the series premiere of the prequel show NCIS: Origins, and appeared in a special Veterans Day crossover episode with the mothership series. He’s also narrated every episode of Origins, which is about Gibbs’ life as a young probationary agent of the Naval Investigative Service (NIS) at Camp Pendleton in the 1990s. Austin Stowell plays this younger version of the character.

​