The Theft of Snape's Personal Stores (Dramatic and Situational Irony)
Professor Snape confronts Harry Potter regarding a recent string of break-ins to his office and private stores. He believes Harry has stolen Gillyweed (which Harry uses to breathe underwater during the second task) and the ingredients for Polyjuice Potion. The irony is that Harry was given the Gillyweed by Dobby, the freed house-elf now employed at Hogwarts. This is dramatic irony because the reader has more information about the situation than Professor Snape, which is why he suspects Harry. There is an additional element of irony because the reader suspects, for a time, that Barty Crouch Sr. is in fact the one stealing from Snape, and this irony is situational in the sense that Barty Crouch is an extremely lawful man, so it would be quite outside his normal pattern of behavior to break into an office and steal.
Harry Becoming a Champion (Situational Irony)
It is ironic that Harry’s name is entered in the Goblet of Fire considering Harry wants nothing more than to be a normal teenager and live a life of relative obscurity like his friend, Ron. The double irony is that Ron wants nothing more than to enjoy the fame and attention that Harry has. There is also an element of situational irony in that Moody, the very professor who vows to protect Harry and figure out who entered his name in the Goblet, is actually the person seeking to harm him and the very person who entered his name. Of course, Moody is not actually Moody, but Crouch Jr. in disguise. But for the majority of the book, the reader does not realize this.
Fred and George Being Sarcastic (Verbal Irony)
When Fred and George ask Ron if they can use his own, he asks them why and Fred says, “Because George wants to invite him to the ball" (159). Of course, the reason they want to borrow the owl is to send a letter. Ron knows that much, but his question is directed towards finding out why or to whom they are sending the letter. Fred instead offers this absurd, sarcastic, and thus verbally ironic remark.
Bertha Jorkins (Dramatic Irony)
Bertha Jorkins goes missing from the Department of Magical Games and Sports. In the first chapter of the book, the reader witnesses Voldemort and Wormtail discussing the murder of Bertha Jorkins. So, every time she's mentioned by Arthur and Percy Weasley, Barty Crouch Sr., and Ludo Bagman, there is a heavy element of dramatic irony because while they fuss over her possible whereabouts, the reader knows that she is, in fact, dead.
