Irony of Love
Nobody in the novel is particularly happy in his or her romantic lives, and many suffer from unrequited love. An emotion that ought to make its possessor happy, love in this novel causes nothing but sorrow.
Captain Phoebus is betrothed to Fleur-de-Lys and eventually weds her and is perfectly miserable. Yet he is briefly attracted to Esmeralda but the relationship is never consummated. In fact, the conflict created by their forbidden love leads to Phoebus being stabbed. Esmeralda is in love with Phoebus, but although he wants to seduce her he does not actually love her back. Esmeralda meanwhile is married to Pierre, whom she saved from the gallows out of pity but whom she does not love. Pierre loves Esmeralda. So do Quasimodo and Claude Frollo.
Irony of Taste
Although the imposing Gothic architecture of Notre Dame cathedral was considered beautiful and impressive in its day, the author depicts it as ugly and backward, particularly after its restoration following the Revolution. The cathedral is a setting for a tale of depravity, inhumanity, and even murder.
Irony of Agnes
Sister Gudule, whose daughter was stolen by a band of Gypsies as a baby, is tormented by the loss of her child Agnes. She discovers that the beautiful Gypsy girl Esmeralda is in fact her lost Agnes moments before Esmeralda/Agnes is executed. She learns the truth too soon to save her daughter.
Irony of Male Attractiveness
The physically attractive men in this story, specifically the vain Captain Phoebus, are shallow and self-serving. The loyal and constant Quasimodo, by contrast, is so physically ugly as to be repulsive to everyone.
Irony of Rescue
When the Gypsies arrive to rescue Esmeralda, Quasimodo believes they are there to harm her, so he drives them away. This was Esmeralda's only real chance of rescue. Frollo's "rescue", in which Pierre participates, was only to give him the opportunity to seduce Esmeralda. When she refuses him, he hands her over to the King's men, whom Quasimodo has been helping in the mistaken belief that they are not trying to catch and execute her.
Irony of Justice
The King, supposedly the ultimate authority and source of justice, orders his soldiers to kill the rioters and the "witch" Esmeralda.
