Jim was born in Youngstown, Ohio, and later moved to New Orleans where he worked on Mardi Gras floats and as a door-to-salesman, he then moved to California where he worked odd jobs before he got into voice acting. Cummings is known for his ability to mimic Sterling Holloway's high voice.
His most notable characters for Disney are Darkwing Duck, Winnie the Pooh, Tigger, Pete, Ray, Bonkers D. Bobcat, Kaa, and various other characters listed below.
In other work outside of Disney, he voiced Steele, the main antagonist of the Universal Pictures animated film Balto, provided additional voices for the stop-motion sketch comedy series Robot Chicken, and voiced Malefor in Season 2 of Skylanders Academy, a role that Mark Hamill originated in The Legend of Spyro: Dawn of the Dragon. He is also well-known for being the current voice of Tony the Tiger in the Kellogg's Frosted Flakes commercials.