Aaron Kelso, known to The Recess Gang and the rest of the Third Street School children as Mr. Kelso, is the friendly local shopkeeper of a corner store named 'Kelso's' which the children visit in numerous episodes. He is kind and often acts as a voice of advice and reason to the kids.
His wife seems more interested in money than in advice, as she seems to henpeck him about turning away business in the name of morality.