Private Fifth Class Arnold "Arnie" Gumble was a member of the Flying Hellfish, Grampa's unit in World War II. He is the father of Barney Gumble. He was in charge of watching his unit's backs inside a tank.
Along with the rest of the unit, he took part in a tontine where the last surviving member would take sole possession of a group of paintings they liberated. He was one of five members of the group to die in a parade float accident in 1979. Apparently, Arnie desired to buy his way into high class society when he took part in the Tontine.