Although a "doctor", Dr. Peanut often exhibited less intelligence and common sense than the not-much-brighter Bobo. He also often irritated the "Lawgiver", Pearl Forrester, with his stupidity and antics, often incurring her wrath.
Dr. Peanut made his final appearance in The Deadly Mantis. Mike inadvertently helped the bomb-worshiping mutants fix their deadly icon and caused the destruction of Earth and Deep Ape; while it appeared Peanut did not escape the blast, the crew of the Satellite of Love receives a letter from him at the end of the episode. Apparently, the bomb caused a time rift and transported him back into the Wisconsin of Earth's past, where he fell in love with and married a member of Mike's family, perhaps leading to the all-simian Earth seen in the future. Just as Deep Ape and the future earth is a reference to Planet of the Apes, and the bomb-worshiping mutants a reference to its sequel Beneath the Planet of the Apes, Dr. Peanut's time travel is a reference to the second sequel, Escape from the Planet of the Apes.