Oppenheimer has voiced many characters, often for Filmation in the 1970s and 1980s, such as Oil Can Harry, Swifty and the narrator on The New Adventures of Mighty Mouse and Heckle & Jeckle, Ming the Merciless on Flash Gordon, the Overlord on BlackStar, Skeletor, Man-At-Arms and Mer-Man from Filmation’s 1980’s cartoon and so many many more.