Martin Brisby

Martin Brisby is the strongest and the eldest son (and second-eldest child) of Mrs. Brisby and a neutral character in The Secret of NIMH and the former main antagonist of The Secret of NIMH 2: Timmy to the Rescue. He is a rude, unenthusiastic, male mouse. He was voiced by Wil Wheaton in the first film, Phillip Van Dyke as an adolescent in the sequel, Eric Idle as his evil self, again in the sequel, and Phillip Glasser as a reformed adult, again in the sequel.

Personality
Martin Brisby is 10 years old (by human age) and is the eldest son of the Brisby family. He is rude and smart-mouthed. He hates it when "Auntie" Shrew comes over to babysit and fights and argues with her. He may somewhat have some similar traits to his father such as personality as well as physical appearance.

Role in Film
Martin is the second child of the Brisby family who dislikes having Auntie Shrew over their house and is not afraid to yell back at her. He claims that he's not afraid of the dark, the farmer, Dragon (the cat), and the Great Owl.

Role in Sequel
Martin is Timmy's brother and son of Mrs. Brisby. He was captured by NIMH. He became insane when the doctors brainwashed him. After being made insane, Martin took over the lab and brainwashed Dr. Valentine with a device similar to the one Valentine used on him and made him think he was a dog. Martin plans to use an army of lab rats riding a flock of ravens to take over Thorn Valley and make Fat Cat and Professor Nimnul rich.

He asks Timmy to join him, but he refuses and is locked in a cage as Martin drags Jenny away to try to make her his queen. Timmy escapes with the help of Cecil and they go to free Jenny. Together, they knock out Martin and Timmy tricks Martin's army of ravens and rats to fly in the wrong direction. Fat Cat betrays Martin, saying that he is an idiot and that he, Fat Cat, does not work well with other people, and was playing the fool to take it all and leaves with Professor Nimnul. Timmy and Jenny then leave to find the others, only to find once everyone is free that NIMH is on fire. The survivors (Timmy, Jenny, and her parents) flee. Timmy goes back to save Martin. Before he leaves, Jenny tells him she loves him and he tells her the same. After being attacked by the crazy cats once again, Timmy sends them down an elevator shaft and finally finds Martin... actually, Martin finds him.

Timmy and Martin are able to escape through the lab's skylight, with some help from Jeremy. Jeremy takes the survivors to safety. Following Fat Cat and Professor Nimnul's defeats, the mice return to Thorn Valley, Martin returns to normal.

Trivia

 * Martin has grey fur, the same fur colour as Jenner.
 * He is similar to Skippy in Robin Hood.
 * In The Secret of NIHM 2: Timmy to the Rescue, Martin is possibly living proof that the chemicals injected into test rats at NIHM, have a small percent chance of driving the subjects insane with increased tendencies of unprovoked aggression and the driven need to dominant others.
 * If this theory is correct, then Jenner would have been the first rodent species to suffer from this side-effect.