Mr. Stratford's Rule
Kat and Bianca's father has a rule that neither daughter is allowed to date, which he amends later in the film, saying that Bianca is allowed to date when Kat dates. Thinking this amendment will keep both daughters from dating altogether, Mr. Stratford is pleased with his parenting strategy. However, this new rule is precisely what leads to both Kat and Bianca becoming involved with Patrick and Joey, respectively. Thus, Mr. Stratford's rule backfires almost as soon as it is put into motion.
The Bribe
The central premise of the narrative is also its deepest irony: Patrick only dates Kat because Joey is paying him to do so, but he eventually starts enjoying Kat's company and falls in love with her. While audiences familiar with the genre of romantic comedy might expect this ending, the characters themselves are unaware of what consequences will come from the complex plot.
The Sonnet
Kat's sonnet that she delivers at the end of the film is an example of irony because it is entitled "10 Thing I Hate About You." In the poem, Kat lists a number of things she detests about an unknown person (although the audience knows she is referring to Patrick), only to end the poem by saying, "I don't hate you, not even a little bit, not even at all." The poem therefore disrupts audience's expectations by showing a version of Kat that they had not seen – one who is not defined by anger but instead by a broken heart.
Bianca's Transformation
Bianca's character trajectory is ironic because, in pursuing her desire to date Joey – the affluent, attractive, and popular boy in school – she actually ends up with Cameron. Furthermore, by the end of the film, Bianca has become more and more like Kat, whom she had earlier in the film despised: Bianca, in a fit of rage and in defense of her sister, punches Joey in the nose at prom. This behavior mirrors Kat's own "injury" of Joey when she intentionally backs into his car in the beginning of the movie.
