Walter Cunnigham Jr. has very little role to play in the novel. In ways he is more of a passive background character to have any important active role. He serves as a way for the readers to get a better insight into the exisitng social classes in Maycomb, where as is later explaiend in the novel, people like the Finches form the top class, followed closely by the Cunnighams who are impoverished farmers, then the Ewells and finally the bottom rung of the class hiearchy is formed by the black community of Maycomb. In many places, Walter acts like a catalyst who faciltates the action in the book, but plays no major part. It is the mention of Walter's name by Scout, which reminds Walter Cunnigham Sr. that he too has a child just like Scout, and helps him regain sanity, and the lynch mob returns with its mission unaccomplished. The inability of Scout's school mistress to understand Walter's reluctance to accept charity show how she is relatively new and unaware of the existing norms in Maycomb which the children take for granted. When Scout invites Walter for lunch, Atticus's understanding gets highlighted. He later tells Scout,
First of all," he said, "if you can learn a simple trick, Scout, you'll get along a lot better with all kinds of folks. You never really understand a person until you consider things from his point of view […] until you climb into his skin and walk around in it.
He talks to Walter about matters like agriculture which Walter can understand and respond to.Thus, it is shown that Atticus treats everyone with the same courtesy and politeness, irrespective of their background. During the same dinner, Calpurnia teaches Scout how she should treat guests.
There's some folks who don't eat like us," she whispered fiercely, "but you ain't called on to contradict 'em at the table when they don't. That boy's yo' comp'ny and if he wants to eat up the table cloth you let him, you hear?" "He ain't company, Cal, he's just a Cunningham-" "Hush your mouth! Don't matter who they are, anybody sets foot in this house's yo' comp'ny, and don't you let me catch you remarkin' on their ways like you was so high and mighty! Yo' folks might be better'n the Cunninghams but it don't count for nothin' the way you're disgracin' 'em – if you can't act fit to eat at the table you can just set here and eat in the kitchen!" This means that when you treat someone like he or she is your inferior it just shows that in reality you are much more inferior than him.
It is important to note that Calpurnia is a coloured woman who teaches Scout ethics and morality, thus proving that it is wrong to assume that African-Americans do not have moral values. Later when Scout wants to call Walter home again, Aunt Alexandra forbids her from doing so because she feels he is not good enough company for Scout. This shows the amount of importance Aunt Alexandra plays to family background and emphasises her difference from Atticus, who treats all men as equal and tries to teach his children to do the same.
Walter hails from Old Sarum, a member of "an enormous and confusing tribe domiciled in the northern part of the county..." Walter is a classmate of Scout's, though he is a bit older and is repeating the first grade. Scout is much larger, though: Walter is a puny boy and his
... face told everybody... he had hookworms. His absence of shoes told them how he got them... Had Walter owned any shoes he would have worn them on the first day of school and then discarded them till mid-winter. He did have on a clean shirt and neatly mended overalls. (Chapter 2)
Scout defends him on the first day of school, trying to explain to him why Walter has no lunch and will not accept any lunch money. But instead of thanking Scout, the teacher, Miss Caroline, "hauled me back to her desk" and "whipped me" with a ruler. Scout blamed Walter for her punishment, and she began her lunch break by "rubbing his nose in the dirt" of the schoolyard. After Jem split them up, admonishing Scout that "You're bigger'n he is," Jem invites Walter to the Finch house for lunch. There, Walter engages Atticus in some adult conversation about farming and then "drowned his dinner in syrup." This time, Scout was chewed out by Calpurnia for being rude to her guest, and she lingered behind as Jem and Walter walked together back to school.
Scout eventually comes to like the shy Walter, and though he never makes another appearance in the book, she does hope to invite him over to her house to play one day. Aunt Alexandra, however, forbids it, believing that Walter is an unfit playmate for her niece "Because--he--is--trash..."