Mister Banjo, aka Kurt Flipots, was hired by the Axis during World War II to be a spy for them. Whenever he had something to report he played his banjo on a popular radio station so that the Japanese forces can decode his secret notes within his music. He later became one of Captain Marvel's earliest foes, however he is only armed with a banjo. He was presumed dead after a fight with Captain Marvel ended with him falling off a boat, however he later turned out to be alive. He later joined the Monster Society of Evil.
In the Robot Chicken DC Comics Special Mr. Banjo appeared in the segment called "Real Characters from the DC Universe" which featured obscure DC villains and heroes and he was the first one. He played his banjo until he was punched by Firestorm. He later participated in the finale battle between the Justice League and the Legion of Doom where he played his banjo in the corner. He continued to play it until a hero yelled at him to stop. He then revealed his banjo to be a concealed gun on the tip and starts shooting but is quickly knocked out by a hero.
In the Robot Chicken DC Comics Special 2 is he shot by a chicken guard.