Cummings has performed on multiple animated series since the 1980s. Among his most famous roles are those of Dimmy in The Snorks, Morton Fizzback and Professor Funt in Denver, the Last Dinosaur, Mr. Hollywood in 2 Stupid Dogs, Doctor Mindbender in G.I. Joe, Clyde Cat in Tom and Jerry Kids, Papa Q. Bear in The Berenstain Bears, Doofus Drake in DuckTales, and he can also be heard as the voice of Sokolov in the Metal Gear Solid video games.