The Dead Don't Have to Turn in Homework (Verbal Irony)
When Sibyll Trelawney predicts Harry’s death, Minerva McGonagall is confident that she is a fraud and Harry is in no immediate danger, so she tells him, "You look in excellent health to me, Potter, so you will excuse me if I don't let you off homework today. I assure you that if you die, you need not hand it in" (109). The irony of her statement is of course that if Harry dies, he wouldn't be able to turn in his homework.
Sirius Black as a Criminal (Situational Irony)
For most of the novel, the wizarding community considers Sirius Black a dangerous criminal who wants to murder Harry Potter to avenge the downfall of Voldemort, when in reality he is Harry's guardian, his godfather, and only wants what is best for him. He was framed for murdering thirteen people and leaking information that led to the murder of Harry's parents.
The Grim (Situational Irony)
At several points, Harry sees signs that encourage him to see the black dog symbolizing as a symbol of death and doom when all along, the dog was protecting him from death. He learns later that his godfather Sirius Black is an unregistered Animagus who transforms into a black dog at will. It is a coincidence that the Grim and Sirius's Animagus are identical.
Sybil Trelawney's Predictions (Dramatic Irony)
The Divination instructor, a witch named Sybil Trelawney, claims to have the ability to predict the future. However, most of her "predictions" are somewhat fraudulent, particularly the ones she demonstrates in class. But while she administers Harry's final exam, she snaps into a trance, her voice changes, and she delivers an ominous monologue about the Dark Lord. Dumbledore says that she "might have been" making a real prediction, which "brings her total of real predictions up to two" (426). After making this supposedly real prediction, Trelawney has absolutely no recollection of it. The irony is that Trelawney pretends to be a real psychic, but only others (and the reader) know that she actually is a real psychic.
