Cummings has performed on multiple animated series since the 1980s. Among his most famous roles are those of Dimmy on The Snorks, Morton Fizzback and Professor Funt on Denver, the Last Dinosaur, Mr. Hollywood, whose catchphrase is "Ain't that cute...BUT IT'S WRONG!!" on 2 Stupid Dogs, Doctor Mindbender, portrayed with an Alsatian accent, on G.I. Joe, the dumb Clyde Cat on Tom and Jerry Kids, Doofus Drake on DuckTales and he can also be heard as the voice of Sokolov in the Metal Gear Solid video games.