Arnold's companion, Ellie spends most of his time in the car listening to a transistor radio. His great dramatic moment is when he offers to pull Connie's telephone cord out, at which point Arnold promptly shuts him up with a barrage of insults (133).
He's even older than Arnold, in his forties. Ellie gives an added charge to Arnold's threats, prepared to accomplish through blunt action what Arnold achieves through verbal finesse. All in all, he's a menacing, mostly silent creep.