David McCallum, who played Donald "Ducky" Mallard on the hit TV show "NCIS," passed away at the age of 90. Ducky was a core cast member from the show's beginning and his presence will be greatly missed. The nickname "Ducky" comes from his last name, Mallard, which is a type of duck. He never protested his nickname and his colleagues often referred to him as such. However, Ducky preferred to use his friends' full names rather than using nicknames.

Only Leroy Jethro Gibbs was allowed to call him "Duck" and in return, Ducky called Gibbs by his middle name. The future of Ducky's character on the show is uncertain, but he leaves behind a wonderful legacy both on and off-screen.