Edward Ends Up Hiring Vivian (Situational Irony)
When Edward picks up Vivian in Phil's car, he is simply looking for directions, and has no interest in soliciting a prostitute. Vivian is the one who makes him engage and drives their interaction. While Edward is undoubtedly feeling disappointed about his recent breakup, he ends up on Hollywood Boulevard almost completely by accident. Thus, it is ironic that when they arrive at the hotel, Edward decides to invite Vivian to his hotel room and spend the night with her. Edward's standards are flexible, influenced by how surprising and charming Vivian is.
Because Edward is initially portrayed as a straight-laced lawyer, his choice to hire a prostitute seems like a departure, and presents some situational irony. As we come to see that Vivian is the "girl-next-door," endearing and wholesome where another woman in her position might be cynical and damaged, a romance blossoms.
The Fairy Tale Ending (Situational Irony)
When Edward offers to bring Vivian to New York and set her up with an apartment, car, and allowance, she rejects him, claiming that his offer is not the fairytale romance she had in mind when she was a little girl. She wants to be swept off her feet, and he feels that he is not ready to make a commitment, given the demands of his work. The end, therefore, can be seen as an instance of irony, because Vivian is so ready to take him back. He arrives carrying flowers, in a limousine, and climbs the fire escape like he is climbing a tower. While there is no discussion of the misunderstanding between the couple—his insistence that she wants an "impossible relationship," her vacillation between wanting independence and protection—his grand gesture is taken as reparative and just what Vivian needs to be swept off her feet. For someone who so adamantly chose independence, Vivian assumes Edward has completely changed in a matter of hours, and accepts her status as his girlfriend without fully identifying what the future has in store for her.
Edward and Vivian Fall in Love (Situational Irony)
Perhaps the most obvious instance of irony is the plot point on which the entire premise of the movie rests: Edward and Vivian end up falling in love with each other. While their entire relationship is set up as a transaction—she is his escort for the week—it ends up becoming complicated when they develop feelings. When Edward hires Vivian, she asks why he is paying for someone when he could just ask a woman out for free. He responds, "I want a professional. I don't need any romantic hassles this week." Ironically enough, romantic hassles are exactly what he ends up with. While neither of them ever thought they could possibly develop a romantic attachment, that is precisely what happens.
Vivian's Social Faux Pas (Dramatic Irony)
Some of the more humorous parts of the film come from the audience's understanding that Vivian is a prostitute who now finds herself in impossibly fancy situations. When Edward takes Vivian to dinner, she meets Morse and his grandson, who view her as a beautiful and elegant woman, but her table manners betray her at various points. She runs to the bathroom upon arriving at the dinner table, causing the men to have to stand immediately after they sit down. She then struggles to remember the various utensils, and sends escargot flying through the air. While Edward and the audience knows that Vivian is unused to such expensive meals, the men who attend the dinner are taken aback—if charmed—by her lack of social grace. Similarly, Vivian is brusque at the polo match and the opera. While the audience knows that Vivian is a prostitute, the characters do not know, and are often taken aback by her rougher and blunter qualities. The audience has privileged information, and one gets the sense that if the characters knew Vivian's profession, they would not be very accepting.
