David McCallum, who played Dr. Donald "Ducky" Mallard on NCIS for all 20 seasons, passed away at the age of 90. As a tribute, CBS aired a photo of McCallum with the text "In Memoriam: David McCallum, 1933-2023" at the conclusion of a marathon of the show's re-airing. McCallum was the last remaining original cast member and was loved by both fans and his coworkers. Former cast member Pauley Perrette posted a heartfelt tribute to McCallum on Instagram, expressing her admiration and love for him. The loss of McCallum will be deeply felt by the NCIS family.