He was voiced by Christopher Knights.
Joining the Toad's henchrats, Fat Barry, along with the others, was presumably kept in the dark about the Toad's plan to eradicate all the citizens of Ratropolis and repopulate it with his tadpole army. He later joined the other henchrats as they discovered Rita on board her ship, The Jammy Dodger, after she had taken back a ruby stolen from her by the Toad. While Whitey restrained Rita and her accomplice, the henchrats searched the ship for the ruby and Fat Barry and Ladykiller Rita's diary, giggling at its entries. Later, the henchrats discover the ruby thanks to Roddy and return to the Toad's headquarters. However, Roddy destroys a great amount of the Toad's collection of valuable objects uncovered in the London Sewers by accident and the henchrats take Roddy and Rita to the Icemaker, a large refrigerator designed to freeze all of Toad's enemies, although the two escape and Spike & Whitey are frozen instead and Rita takes back the ruby once more. Later, Spike formulates a plan to capture Roddy and Rita by pursuing them on the Ratmobiles, a group of kitchen appliances (primarily hand mixers) designed to travel across water. Locating the Jammy Dodger based on Thimblenose Ted's information from a reconnaissance mission, Spike issues the order to attack. During the chase, Rita dumps a batch of custard powder into the water from the ship. Not knowing what it is, Fat Barry accelerates his Ratmobile, causing the hand mixer to mix the powder together and envelop the rat in a custard swirl. After being freed, Fat Barry later returned to fight Roddy and Rita again alongside the other henchrats when Roddy attempted to rescue Rita, who had been captured earlier by Whitey and Spike. Subduing the two eventually, the Toad reveals his plan and Roddy, in order to stop the Toad, breaks a nearby nitrogen tube, distracting all of the henchrats in a frenzy. During the chaos, Ladykiller gets hit by the liquid nitrogen tube and gets frozen and Fat Barry collides with him, causing the two rats to fall over a ledge.