Clueless is better known for its connections to Jane Austen than its Shakespeare references; however, one of the means it uses to convey the plot of Emma is Shakespeare.
I detected two Shakespeare allusions in my admittedly-hurried glance through the film, and they're the most telling for the way they contrast. In the first, the Cher Horowitz / Emma Woodhouse character rightly recognizes lines from Shakespeare's Sonnet 18 as "famous"—but doesn't attribute them to Shakespeare. By the time, much later in the film, that the second allusion comes along, Cher / Emma has grown—and the male lead starts to recognize something more in her thereby:
That Mel Gibson provides her with this ability to recognize what the character of Hamlet said or didn't say is immaterial—she has the knowledge, and she's able to employ it. And it's also a good sign that she attributes the quote to "that Polonius guy" instead of "that Ian Holm guy."
Links: The Film at IMDB.