David McCallum, who portrayed the wise and eccentric Dr. Donald “Ducky” Mallard, was a cornerstone of the series since 2003. He passed away on September 25, 2023, at the age of 90, after a rich career as a musician and author, in addition to his iconic role. Ralph Waite, who played Jackson Gibbs, the steadfast father figure, died on February 13, 2014, at 85, remembered for his warmth and authority.