Like Billy, Harold is very stupid and is prone to do stupid things. It seems he is an expert in dancing as in the episode Billy Idiot, he beat Mrs. Pollywinkle, who was Billy's dance teacher. He sees Billy as a genius due to the boy's "genius" when Billy was young and tries to get others to see this too, as seen in The Problem with Billy, much to Billy's irritation. Despite this, he still gets annoyed sometimes by Billy's antics. He is afraid of Santa Claus and his wife, Gladys, who is mentally unbalanced.
Harold is a voracious eater, and he is willing to eat anything. He once said that he was still so hungry after eating two breakfasts that he couldn't wait 'til lunch and so knowingly ate his wife's mucus covered pet rat live. He also ate his wife's goldfish but for the reason that only his wife heard and not Billy, Mandy, Grim or the audience.
Harold has the same facial shape and large pink nose as his son. He wears blue pants and an a white t-shirt with orange sleeves. He is also very fat, thus, his stomach bulges out of his shirt. He is also shown in some episodes to be very hairy and disgusting. Harold has 2 and a half feet, as he has half a foot growing out of his right foot.