In Part One, McMurphy vies with Harding for the unofficial position of lead patient. Harding uses an allusion and verbal irony to poke fun of McMurphy:
"As you see, all these natural talents certainly qualify you as a competent therapist and render you quite capable of criticizing Miss Ratched’s meeting procedure, in spite of the fact that she is a highly regarded psychiatric nurse with twenty years in the field. Yes, with your talent, my friend, you could work subconscious miracles, soothe the aching id and heal the wounded superego. You could probably bring about a cure for the whole ward, Vegetables and all, in six short months ladies and gentlemen or your money back."
McMurphy has just suggested that Harding shouldn't have to put up with the way Nurse Ratched leads the other patients in analyzing and criticizing him. She calls it "therapeutic" for Harding, but McMurphy isn't so sure it accomplishes anything except emasculating Harding. Harding defends Nurse Ratched, and by extension his own willingness to put up with the criticism. Here, he alludes to the Freudian concepts of the "id" and the "superego" as he sarcastically suggests that McMurphy is better qualified than the hospital staff to treat the patients on the ward. According to Freud, the id is the part of the psyche that gives us animal instincts and desires. The superego, meanwhile, is the part of the psyche that gives us morals. The ego is the third part, the self that tries to balance the warring interests of the id and superego. Harding states that of course McMurphy can "work subconscious miracles" on the id and superego, miracles the likes of which Nurse Ratched could only dream.
Of course, Harding means exactly the opposite of what he says: McMurphy has no qualifications to treat mental illness. He borrows the line "six short months ladies and gentlemen or your money back" from the language of snake-oil salesmen who peddle fake cure-alls to carnival audiences. This reference makes it abundantly clear that Harding believes McMurphy is all talk. Who is he to criticize Nurse Ratched's tactics, Harding obliquely suggests, if he has no better solution to the patients' struggles? The verbal irony makes McMurphy look laughably foolish.
Harding's tone is light and mocking, but his allusion to Freud betrays deeper-seated turmoil. Freud's theories, which have been more and more regarded as oversimplifications of human psychology, were especially forced onto gay men like Harding in the mid-20th century. Society told gay men that they needed to master their "urges," bringing the id under control of the superego to live a heterosexual life. This self-denial was incredibly harmful, leading to what Harding characterizes as an "aching id" and a "wounded superego." Notably, Harding does not mention the ego, which in Freudian term is the real, decision-making self. Harding has spent his life torn between the person he is and the person everyone wants him to be. In that struggle, he has lost his sense of self and his sense that he has control over his own life. He believes that Nurse Ratched is trying to help him, but really she is tearing him further apart. The idea that McMurphy could come in and soothe this pain in one fell swoop is inconceivable to Harding.
In Part Four, Nurse Ratched sends Bromden and McMurphy to receive electroshock therapy. McMurphy goes first, using verbal irony and an allusion to make light of the scary situation:
He don’t look a bit scared. He keeps grinning at me.
They put the graphite salve on his temples. “What is it?” he says. “Conductant,” the technician says. “Anointest my head with conductant. Do I get a crown of thorns?”
They smear it on. He’s singing to them, makes their hands shake.
McMurphy, who is lying on a cross-shaped table to receive the treatment, is referring to the Christian story of Jesus Christ's crucifixion. Before Jesus was crucified, Roman soldiers supposedly dressed him in purple (a color associated with royalty) and placed a crown made out of thorns on his head. They mocked him for being "king of the Jews." The outfit was meant to parody a true royal outfit and to disempower Jesus and his followers by making clear that he would never be a "real" king. However, the parody backfired. Jesus is often depicted wearing a crown of thorns, and the crown itself has become a major symbol of Jesus's power and martyrdom.
McMurphy often uses humor, especially verbal irony, to stand up to power and cruelty, which is what he does in this scene. The hospital staff is about to pin McMurphy down and inflict brain damage on him. Though he doesn't show fear, McMurphy knows he has lost his power struggle with the hospital staff in almost every way that counts. He is utterly at their disposal, and practically no one cares what they do to him. By using faux-Christian language (i.e. "annointest") and asking if he is going to be given a crown of thorns, he absurdly suggests that he is as powerful, important, and righteous as Jesus. He does not actually believe any of this. However, his verbal irony lets the hospital staff know that they cannot take away his laughter or swaggering attitude.
Even though McMurphy does not believe he is Jesus, there is a way in which he does serve as a Christ-like figure to Bromden and the other men on the ward. McMurphy shows the men that they can take their dignity back, and that there is a world beyond the hospital that they might like to rejoin. Like Jesus, he ultimately dies so that his "followers" can live outside the oppressive regime of Nurse Ratched.