Jenner is the main antagonist of the 1982 animated adaptation of Mrs. Brisby And The Rats of NIMH, known as The Secret of NIMH. He is a manipulative, power-hungry, heartless, selfish, and evil rat of NIMH who betrayed his own kind due to his desire to remain in the rose bush, rather than leave to a better life in Thorn Valley, as promised by their leader, the old and wise Nicodemus. He was voiced by the late Paul Shenar, who later played Alejandro Sosa.