During a career that spanned five decades, Mars appeared in more than 35 films, including "Butch Cassidy and the Sundance Kid" (1969), "Desperate Characters" (1971), "What's Up, Doc?" (1972), and "Radio Days" (1987). He also had roles in scores of television shows, including "Love, American Style," "Fernwood Tonight, "The Ghost and Mrs. Muir," "McMillan & Wife" and "Malcolm in the Middle."
In "The Producers" (1968), he played Franz Liebkind, a somewhat demented Nazi whose play, "Springtime for Hitler," attracts a couple of scheming Broadway producers played by Gene Wilder and Zero Mostel. One of his most quoted lines was, "Not many people know it, but the Fuhrer was a terrific dancer!"
In "Young Frankenstein," Mars again displayed a flair for Germanic characters in the role of Inspector Kemp, a monocled police chief with a hilariously malfunctioning prosthetic arm.