At the end of Chapter 13, after she and her friends defeat the Wicked Witch of the West, Dorothy finds and takes the Golden Cap. This moment contains dramatic irony and foreshadows the way Dorothy and her friends will all make it to their respective homes:
Dorothy went to the Witch’s cupboard to fill her basket with food for the journey, and there she saw the Golden Cap. She tried it on her own head and found that it fitted her exactly. She did not know anything about the charm of the Golden Cap, but she saw that it was pretty, so she made up her mind to wear it and carry her sun-bonnet in the basket.
Dorothy does not realize, as the narrator and reader do, that the Golden Cap allowed the Wicked Witch of the West to call the Winged Monkeys to do her bidding. She takes it to wear instead of her sun-bonnet, thinking only that she likes the look of it. Because the narrator has already described the "charm of the Golden Cap," this moment seems far more significant to the reader than to Dorothy. It seems all-but-certain that Dorothy is going to call the Winged Monkeys at some point (likely three times) before the story is over.
That is exactly what happens. Dorothy first calls the Winged Monkeys to carry her and her friends back to the Emerald City. The reason they need help reaching it is because they don't know their way out of the Wicked Witch's country: they can't retrace their steps because she had the Winged Monkeys capture them and carry them to her castle. This first use of the Golden Cap demonstrates that it and the Winged Monkeys are neither inherently good nor inherently evil. They are simply tools that can be put to use for any number of purposes. The Wicked Witch uses them to control others, but Dorothy uses them only to help herself and her friends make it where they need to go.
Dorothy's second request of the Winged Monkeys turns out to be out of the scope of what they can do, but her third request brings her and her friends to Glinda. Just as the Wicked Witch was evil, Glinda is an unquestionable force of good. She takes the cap from Dorothy and also uses its charm to call on the Winged Monkeys for their aid to help all the characters find their way home. But after they have done what she asks, she plans to free them so that they too can enjoy their lives wherever they belong. Glinda's choice to liberate the Winged Monkeys from the charm of the Golden Cap demonstrates that the ultimate good is for everyone to be free to live their own lives.
In Chapter 18, Dorothy is distraught to learn that the Winged Monkeys cannot take her to Kansas and that by asking them to do so, she has wasted one of her three allotted wishes of them. The Scarecrow immediately begins thinking about what to do next, and Baum uses absurd imagery that highlights the situational irony of the Scarecrow's belief that the Wizard has made his brain more functional:
‘I have wasted the charm of the Golden Cap to no purpose,’ she said, ‘for the Winged Monkeys cannot help me.’
‘It is certainly too bad!’ said the tender-hearted Woodman.
The Scarecrow was thinking again, and his head bulged out so horribly that Dorothy feared it would burst.
The image of the Scarecrow's grotesquely bulging head is "horrible" to Dorothy, but it is laughable to the reader. The Scarecrow spent the first two thirds of the book convinced that his head was empty. Despite this belief, he was the main strategist among Dorothy's friends all along. For example, it was the Scarecrow who thought of the plan to enlist the field mice to help save the Cowardly Lion from the field of poppies. Now that Oz has filled his head with bran (not even real brains), the Scarecrow is still strategizing the same as ever. The only difference is that now, his head keeps bulging out dangerously and comically. It is ironic that the Scarecrow thinks he is better off now when, in fact, he seems to have more in his head than can fit. He would really have been better off if he had started believing in himself instead of insisting that he needed the Wizard to overstuff his head.
In Chapter 19, Dorothy and her friends venture to the South after Oz has left in his balloon. They have a conversation about Oz that is driven by dramatic irony, and this irony serves to gently satirize naive followers of manipulative leaders:
‘Oz was not such a bad Wizard, after all,’ said the Tin Woodman, as he felt his heart rattling around in his breast.
‘He knew how to give me brains, and very good brains, too,’ said the Scarecrow.
‘If Oz had taken a dose of the same courage he gave me,’ added the Lion, ‘he would have been a brave man.’
Dorothy said nothing. Oz had not kept the promise he made her but he had done his best, so she forgave him. As he said, he was a good man, even if he was a bad Wizard.
Dorothy and the reader realize what the Tin Woodman, the Scarecrow, and the Lion do not: Oz is not a wizard at all, and he did not use magic to solve their problems. Dorothy is frustrated with him for failing to help her. Still, his failure allows her to see him as the fallible human character he is. Whereas the others believe that he has all the answers in the world, Dorothy sees that he simply tricked them into finding their own answers. She does not think this manipulation makes Oz a bad person because ultimately, the Woodman, Scarecrow, and Lion gained much-needed self-confidence. But she is nonetheless frustrated that he led her to believe he could do magic and then let her down.
Although the book treats the Woodman, Scarecrow, and Lion lovingly, this scene portrays them as a bit foolish. Even if they have gotten what they needed through their interaction with Oz, they haven't learned the key lesson Dorothy has learned: no one is all-powerful, and we usually have to find our own answers to life's difficult conundrums. Whether or not Baum intends it, the book satirizes people who blindly believe in powerful people's leadership and wisdom. This critique evokes some of the key tenets of the Populist movement of the 1890s. This movement aimed to divest corporations of power, instead putting it into the collective hands of farmers and laborers.
