If you are only familier with him as Ducky on NCIS then it may be a surprise to you that David McCallum was something of a sex symbol in the 1960's. He was the co-star of the spy drama "The Man From U.N.C.L.E." He played Russian agent Illya Kuryakin. He almost didn't get on the show. After the network viewed the pilot they asked that one actor be recast. The Network was referring to Mr. McCallum. The series creator and producer was thinking of recasting the agents boss Mr. Waverly and thought they ment him. So there was no arguement with the request. The executives were surprised to later see Mr. McCallum in the first show. When teenage girls became fans of the show as they were attracted to him the ratings went up and made the show a hit.
Years later,after the show left the air, the creator of the show met one of the network executives at a party. They finally talked about the mix up. The network executive said it was the best mistake that was ever made for the network. Below is an ad for a pin-up that was selling in comic books and magazines at that time.