The Handicapped Campers are the 4 kids that Steve gets put in charge of counseling in the Season 3 episode Camping Ain't Easy.
They are all physically or genetically disabled. One has dwarfism and progeria, the second has low blood sugar, being paralyzed amid countless complications (and was voiced by the late Eric the Actor), the third has an albino pigmentation and vulnerability to sunlight and the fourth is a blind Puerto Rican, who was shocked by his ethnicity as his parents told him he was Japanese.
At the end, Steve killed them off just like he did with his first four campers when he knocked over a pair of wooden poles that crushed them, killing the albino, blind and progerian ones with one pole while the wheelchair one tried running but still got crushed by another pole. In an attempt to "undead" them, Steve put their corpses in a cursed burial ground and they came back as zombies.