The Fat camper is a member of Junior Campers.
After Bart Simpson had tried to run away from the room, his scarf was stuck in the door and he almost strangled himself. When he woke up, the fat camper was just doing artificial respiration to him and Bart angrily throw the camper away.
When Ned Flanders told the campers to take their knives out, excited Bart caught the fat camper's one and the scared camper told Bart, "Don't hurt me!"
When the rafts were separated, the fat camper was in the group of campers that stayed with Ernest Borgnine. They ended up being stalked and attacked by a mysterious person or creature while they were sheltering at an old abandoned summer camp. What happened to them after that isn't known.