Virginia's marriage (Dramatic Irony)
Virginia's marriage is ironic because it shows the Otis family becoming embedded within the English aristocracy. For much of the story, it seems like the Otis family has a totally different approach and life philosophy, and that the point of the story if to contrast how different Americans and Europeans are. However, the happy marriage between Virginia and the Duke shows that both groups can get along, and that even if they make fun of them, European aristocrats are not going to be able to survive without the Americans. Virginia's marriage ensures that an aristocratic bloodline will continue through the children she will presumably have, but those children are now ironically going to be connected to America and American values.
The ghost's conscientiousness (Situational Irony)
Ghosts are usually seen as lawless and defiant of rules and expectations: they defy the basic expectation of the dead not returning to the land of the living, and because of their supernatural powers, they cannot easily be banished or defeated. While the Canterville Ghost certainly does not like being told what to do, he ironically does feel very compelled to maintain his honor and integrity. For him, this is connected to fulfilling certain tasks like maintaining the bloodstain and haunting the halls at certain times. Even though more than 300 years have gone by, the ghost has never questioned his duty to continue to uphold traditions and do things the way he has always done them. Ironically, a figure for whom rules or laws no longer apply is far more concerned with following protocol than the actual humans around him are. As Lydia R. Wilburn notes, "Wilde succeeds in upending conventional notions of good and evil when he elicits from the reader some sympathy for the Ghost who had committed a crime but who is responsible, concerned for others, and polite" (Wilburn, pg. 49).
The ghost is asked to oil the chains (Situational Irony)
When Mr. Otis first encounters the ghost, he is annoyed by the sound of the clanking chains and suggests that the ghost oil the chains to make them less noisy. This suggestion is ironic because it inverts the expected power dynamic between the ghost and his victim. In most ghost stories, the specter is the one who holds the power by frightening and threatening their human victim; the person who is targeted by the ghost is usually at their mercy, and inclined to do whatever they are told. Because he is not afraid of the ghost, Mr. Otis does not take on the role of the victim, and it is the ghost who ends up being intimidated and told what to do.
The Canterville Ghost is scared of another ghost (Dramatic Irony)
When the Canterville Ghost encounters the fake ghost the twins have set up to fool him, he is deceived into thinking it is another ghost like him. More importantly, and ironically, he is terrified of this other ghost: he has exactly the reaction that the Otis family was expected to have when he first started haunting them. Even though it seems like he should be aware of the tricks and techniques used to inspire fear, the ghost still falls for it.
