Humor sometimes results from the disparity between the child’s experience of the event—and her language-- and the adult’s dry tone in reporting it. I just finished reading the conclusion again, and found something very humorous in Scouts screaming “Cecil Jacobs is a big wet he-en!” with the narrator saying nothing about the silliness of this, complicated by the frightening context created by the fact that we the audience know this is not Cecil following the children home. Scout pretty much knows this too, but handles her fear with this childish way of controlling it. The absurd notion of her caught in the armature of a ham costume adds to the humor, edged by the suspense of the situation. Their discussions of Boo at the beginning of the story are full of the language of childhood, perhaps universal childhood, but in the background again is the more knowing and sophisticated voice of the adult reporting this with, we might imagine, a smile on her face. Their game over touching the gate to Boo’s house is an example. Jem says (terrified himself), “See there” Jem was scowling triumphantly. Nothin to it. I swear, Scout, sometimes you act so much like a girl it’s mortifiyin’.” Of course she acts like a girl for she is one! This distance between the two narrative voices, that of the child and that of the adult, is a form of irony.
I think Scout can be quite funny. She has a quick wit and a fearlessness that is endearing. Think about the incident with her teacher in Chapter Two, in which Scout tells Miss Caroline that her brother Jem believes she was switched at birth and that she could read the newspaper as soon as she was born.
Other humorous incidents include Atticus' indulgent but amused listening to the problems of childhood, and the childish games Dill, Scout, and Jem play when they challenge one another to approach the Radley home.
Although the novel is serious, the lightness of childhood, with all of its innocence and playfullness, is infused throughout.