In 2011, Newhart made a guest appearance on the “NCIS” episode, “Recruited” (via TV Goodness). He took on the role of Dr. Walter Magnus who was Dr. Donald Mallard — aka Ducky’s — predecessor at NCIS. While he brought some humor to the role, his character was a tragic one. Older in age, he was dealing with Alzheimer’s. He told Ducky that his wife had passed away and he had become estranged from his daughter. Eventually, it was discovered that he was living with his daughter and her family. When he zoned out and got disoriented working with Ducky, it became clear that he was suffering from the illness.
While the role was more serious than fans were used to seeing Newhart take on, he did have some humorous lines (via IMDb). Most notably, telling Special Agent DiNozzo that he was excited to be back in autopsy. DiNozzo replied that the room was smelly from the dead bodies, but Newhart quipped that it was “a matter of opinion.”