Dudley's Gang (Dramatic and Situational Irony)
Dudley tells his parents he is having tea with a different friend, or member of his gang, every day. In actuality, he and his gang are vandalizing the local park, smoking, throwing rocks at cars and children, and bullying younger children. The dramatic irony is that the reader knows full well that Dudley is not having tea, even as the Dursleys talk about it in their house. Situationally, Dudley exactly defies the superficial image of "polite society" that his parents expect of themselves and their neighbors.
I Must Not Tell Lies (Situational Irony)
When Harry is in detention with Professor Umbridge, she has him write, "I must not tell lies." It is ironic since Harry is not the one lying. Umbridge is perpetuating the lie that Voldemort has not returned. By refusing to admit to Voldemort's return and continuously reassuring the public that everything is okay, the Ministry of Magic is lying. Yet Harry is punished for stating the truth.
Hermione's Clothes (Situational Irony)
Hermione starts S.P.E.W. to improve the conditions for and treatment of house-elves. A part of this involves her knitting clothes for the house-elves and hiding them in the Gryffindor common room. Ironically the house-elves do not appreciate this gesture, and they stop cleaning the Gryffindor towers except for Dobby.
The Sorting Hat Defies Its Purpose (Situational Irony)
It is ironic that the Sorting Hat's song states that the houses must unite, even while sorting students into separate houses. It is recognizes the danger of its sorting and hopes that the students will embrace each other's differences and unite rather than dwell on their differences and remain separate.
