David McCallum, renowned for his role as Dr. Donald “Ducky” Mallard, graced the series from 2003 until his death at 90 in 2023. Born in Glasgow, Scotland, his extensive research and musical background enriched his portrayal, making him a beloved character. Similarly, Ralph Waite, known for his role as Jackson Gibbs, brought warmth and depth to the show until his passing in 2014 at the age of 85.