Brutus

Brutus is a rat who is guard in The Secret of NIMH. He is first seen when Mrs. Brisby is at the entrance he greets her with his battle ax and she asks him if he's Nicodemus but instead he does not answer he's chases her back the way she came despite being scary and brutal Brutus actually turned out to be a good guy he is seen in the sequel as Timmy's babysitter giving him a whistle.