"I'm a Normal Teenage Girl" (Situational Irony)
In the opening scene, Cher claims to "actually have a way normal life for a teenage girl. I mean I get up, I brush my teeth, and I pick out my school clothes." Immediately following this, the camera flashes to her picking out her outfit on a customized computer program and pulling designer outfits from a palatial closet. While Cher thinks she is a normal girl, it is clear that she is exceptionally wealthy and privileged. The irony of Cher's lack of self-awareness about her own entitlement is played for laughs throughout the film.
"Clueless" (Situational Irony)
In addition to her lack of self-awareness about her own privilege, Cher is often in the dark about her own personal life, in spite of thinking she has a sturdy handle on things. The title itself strikes an ironic tone, because while in Cher's understanding it is everyone around her that is "clueless," she realizes late in the film that she is, too. Cher's blind confidence about her own abilities and intuition is challenged when she misreads Elton's interest in Tai, when she is unable to identify Christian's sexuality, when she fails her driving test, and most importantly, when she barely notices her mounting attraction to Josh.
Cher's Grades (Situational Irony)
There is a great deal of irony contained in the way that Cher goes about raising her grades. Rather than work harder in her classes, the logical way to raise one's grades, she feels that the only course of action is to get involved in her teachers' personal lives and set about matchmaking in order to negotiate for revised grades. When she shows her father her report card, he looks at the revised grades skeptically, and for a moment, the viewer expects him to chastise Cher for resorting to manipulative rather than honest academic tactics. However, he is proud of Cher for gaming the system and arguing her way to a better GPA. His response is not what we expect from a parent and this irony is encapsulated in his praise: "Honey, I couldn't be happier than if they were based on real grades."
Cher's Grasp of Literature (Situational Irony)
When Dionne and Cher are trying to set up Mr. Hall and Ms. Geist, Cher writes a romantic quote in the letter that she puts in Ms. Geist's mailbox at school. When Dionne asks if she wrote the quote, Cher assures her that it's a "famous quote"... from "Cliffnotes." The quote Cher picks is perfect and romantic, sending Ms. Geist into a romantic daze, even though Cher has misattributed a famous line of Shakespeare to an academic guide.
Similarly, when Josh and his date are discussing Shakespeare's Hamlet, Cher corrects the date's misattribution of a quote from Hamlet. Even though she has never read the play, Cher correctly knows—from the Mel Gibson movie—that "that Polonius guy," not Hamlet, says "To thine own self be true." Cher's knowledge about Mel Gibson and pop culture allow her to outsmart a self-important undergraduate intellectual. The irony is that through her savant-like knowledge of pop culture, Cher proves herself to be intelligent and discerning, even if she didn't actually do the reading.