Rat is a tall, even taller figure than Mr. Fox and most other animals in the film. He's extremely thin, giving him a resemblance to Bean. Rat has black fur and gleaming red eyes, with ears bearing numerous tears and scars. He wears a red and white striped shirt and long black trousers.
Franklin Bean's personal security guard, Rat is a southern accented rat that lives in Bean's apple cider cellar, guarding the cider from trespassers. He is shown to have some kind of connection with Mr. Fox when he comes to steal cider from Bean's cellar. Rat carries a switchblade knife, which he is about to use against Fox before Kristofferson pulls a rug out from under his feet and sends Rat sprawling into an apple crate, then slams the lid shut on him.
Rat shows up again in the sewers after Mr. Fox and company have been flushed out with cider. He informs the group that Bean has Kristofferson, mistaking him for Mr. Fox's son, but then Ash shows up, revealing himself as Fox's true son. Ash tries to fight against Rat but gets easily overpowered and thrown into the wall. Rat then makes way for him with a sack in his hands. Before Rat can take Ash, Mrs. Fox arrives, knocking down Rat, who briefly flirts with her before shoving her out of the way and successfully trapping Ash in the sack. Then, Mr. Fox appears and tackles Rat, sending the duo into a confined space near an electric fence, which Rat touches and gets electrocuted. In his last moments, he gives them Kristofferson's location, which Ash considers his redemption. Mr. Fox agrees with his son, but sorrows in that he'll just be "another dead rat in the garbage pail behind a Chinese restaurant." Rat's body is then spirited away along the sewer water.
- Rat's role in the original book is considerably shorter, as he's met in Bean's cider, sipping from a large jug. He apparently has no connection with Bean, only wishing to be left alone. His attitude is more rude, given that he's in a drunken state. He is also more cowardly, as Mr. Fox threatens to eat him should he interfere with the fox's thieving.