Billy is a dim-witted, happy-go-lucky boy, who is best friends with The Grim Reaper and childhood friend / neighbor Mandy. His IQ is -5.
Billy can be best described as the embodiment of both adages: "Glutton for Punishment" and "Ignorance is Bliss".
Billy is..to say the least, an idiot, whose IQ is -5 (The same IQ test taken by a shovel and two candy bracelets, they scored 17) which is a level well below even the greatest degree of mental retardation and even animals. It is thought that he get's this trait of stupidity as well as his looks from his father Harold, while he has likewise inherited his mother Gladys' craziness and aggression. His intelligence changes from episode to episode, ranging from being less than average to not understanding the most basic of concepts such as eating, leaving him wondering why the bread he's eating gets smaller every time he takes a bite.