Generally, dogs are hostile to Jimmy. When they see him, they will run in a rapid circle around him, then head towards him and attempt to bite his wrist. If the bite connects, Jimmy takes moderate damage, and knocks the dog loose by cuffing it on the side of the head. Jimmy can either kick the dogs or attack them with any of his ranged weapons such as the Slingshot or Bottle Rocket Launcher. A dog runs away after a single attack. They have a life bar, but can't be knocked out - their health won't drop below 1.
Dogs feature several different places in the game. During Photography 3, Jimmy can take pictures of dogs in New Coventry for his assignment. Dogs are rare in New Coventry, however. They most often appear in Blue Skies Industrial Park and Bullworth Vale, in the residential neighborhood.
During the course of the game, Jimmy is hired by two different townsfolk to find their runaway dogs. They follow him back to their owners when he calls them. They also appear when Jimmy runs the Paper Route, although they can't hurt him while he's on the bike and he can "attack" them by hitting them with the front wheel of the bike.
A Doberman is listed in the game data files but does not appear. Sometimes an adult will chase Jimmy if he attacks their dog, which will be walking in front of him or her.
If a dog attacks Jimmy while he has allies nearby, they will run after the dog and attempt to attack it if they catch up to it. If they do enough damage to make the dog run away, they'll try to chase it but be unable to keep up with it.
Chester is a dog belonging to Chad Morris. Although Chester isn't graphically distinct from any other dog, he does play a role in the story. At almost all times he can be found in the small grassy sideyard by Harrington House, and he'll attack Jimmy if he gets close. During The Big Prank, Gary uses Chester for a prank. He induces Chester to eat rotten meat, then when Chester defecates, Gary stores the feces in a paper bag.
If Jimmy is in good standing with the Preppies and Chester attacks him, most of the Preppies will try to attack Chester. Chad, however, won't.