Mark Harmon’s iconic character, Leroy Jethro Gibbs, was notably absent from the Ducky-centric episode in NCIS Season 21, leaving fans curious about his non-appearance. The real reason behind Harmon’s absence stems from his departure from the show in Season 19, where his character retired to Alaska, marking a significant shift for both the actor and the series. Although Harmon’s return was highly anticipated for this special episode honoring David McCallum’s Dr. Donald “Ducky” Mallard, scheduling conflicts and Harmon’s desire to explore other opportunities prevented his appearance. This decision underscores the show’s ongoing transition and evolution without its longtime lead, reflecting both logistical challenges and creative choices as NCIS continues to move forward.