Irony of friendship
Arrietty, who like many teenagers is bored, curious, and a little bit lonely, tries to expand her world by making friends with the Boy, one of the gigantic "human beans" but the discovery leads to the loss of the only home she has ever known.
Irony of superiority
Pod and his family believe themselves inherently superior to the "big" people but their "borrowings" are interpreted as theft, which the larger people believe to be morally wrong.
Irony of normalcy
The members of the Clock family see themselves as normal and the "big" people as abnormally huge, odd, and ungainly. Yet the children never encounter other people of their own kind. In reality, there are more "big" people living in the house than there are Borrowers.
Irony of education
By helping the Boy learn to read, Arrietty believes she is instructing him from a position of superior education and intelligence. Yet the gaps in her own education are revealed when the Boy describes "millions" of other big people and Arrietty realizes she cannot vouch for the existence of any Borrowers besides her own family, having never seen any of them in person.
Irony of self reliance
Pod and his family believe they live a self-sufficient hunter-gatherer lifestyle, relying on their "borrowing" efforts to provide themselves with food, clothing, and even shelter. They feel quite self-sufficient and resourceful. Yet in reality they are parasites. Everything they own comes from the labor and efforts of the much larger "human beans" they mistrust and despise.
