David McCallum has played the role of Dr. Donald Mallard in "JAG," "NCIS" and "NCIS: New Orleans," and Illya Kuryakin in "The Man from U.N.C.L.E." McCallum has also appeared in many other roles on different television shows.
McCallum has played Mallard since his first appearance in a 2003 episode of "JAG," and he played Kuryakin from 1964 to 1968. In addition to these roles, McCallum has appeared in many other shows. He played Walter Thornhill in "The Education of Max Bickford," and Dr. Daniel Weston in "The Invisible Man." McCallum has also done voice roles, guest starring as Merlin Ambrosius in "Batman: The Brave and the Bold."