Walter Tetley as Julius Abruzio was the Grocery delivery boy, and since he drove the delivery truck, he was taken to be about 17 or 18 years old. Maybe he played it with a little lower voice, because you believed it. He would always show up at just the right moment to get clobbered by Phil and Frankie.
Frankie: "I don't think that this formula will turn a man invisible"
Phil: "Well where could we find someone to test it on?"
Julius (off stage) "Hey where is everybody, I brung the groceries!"
Phil: "Well if it isn't little ginuea pig Abruzio!"