In Part One, Bromden introduces Nurse Ratched not as a human, but as a machine "big as a tractor" who can disguise herself as a human. When the other patients come out of their dorms, there is an interesting interplay between dramatic irony and Bromden's status as an unreliable narrator:
[S]he has to change back before she’s caught in the shape of her hideous real self. By the time the patients get their eyes rubbed to where they can halfway see what the racket’s about, all they see is the head nurse, smiling and calm and cold as usual [...]
Bromden insists that there is dramatic irony at play: none of the other patients know what he knows about Nurse Ratched. He can see her "hideous real self" as a giant machine because she never notices that he is there to witness her take this shape. As soon as other patients are around, Nurse Ratched once again shape-shifts into the "smiling and calm and cold" nurse they all see her as.
Bromden understands that he hallucinates and that not everything he remembers from the mental hospital really happened. This is one moment where the reader can easily see that Bromden is caught in a delusion. This book is not a work of fantasy or science fiction, and the real world does not allow for humans and machines to transform into one another in the way Bromden describes. Nevertheless, he insists that he is being truthful in his account. Searching for the grain of truth in this scene, it becomes clear that he really does see something about the nurse that others fail to see. He understands the nurse as one piece in the Combine, the giant social machine that preys on people like him and the other patients. The nurse may not physically shape-shift, but Bromden identifies her as one of the moving parts in a huge system built on human suffering. This means that while she is one of the primary villains in all the men's stories, the real cause of their suffering is much larger than her. Were she to be removed from her position, she could easily be replaced. Rising up against what she represents will require completely dismantling the social systems that have failed the men on the ward.
In Part Three, Bromden wants to sign up for McMurphy's fishing expedition but is afraid to do so because of the dramatic irony he has maintained so long around his hearing. He is amused by the situational irony:
[I]t’d show I’d been hearing everything else that’d been said in confidence around me for the past ten years. And if the Big Nurse found out about that, that I’d heard all the scheming and treachery that had gone on when she didn’t think anybody was listening, she’d hunt me down with an electric saw, fix me where she knew I was deaf and dumb. Bad as I wanted to go, it still made me smile a little to think about it: I had to keep on acting deaf if I wanted to hear at all.
Bromden has faked his own deafness for years as an act of self-preservation. It allows him to fade into the background and collect ammunition against the hospital staff without anyone noticing. Now, this decision is backfiring on him. He realizes that in order to get what he wants (a spot on the fishing expedition) he would have to reveal his secret and make Nurse Ratched so angry that she would surgically debilitate him, making sure he could never hear or speak again. Ironically, a decision made out of self-preservation has put Bromden at great risk.
The fact that Bromden wants to go on the fishing expedition is testament to the change McMurphy has brought to the ward. Bromden has always disappeared into his hallucinations of fog, and the idea of leaving the hospital has only just started to occur to him. More than that though, Bromden's smile suggests that he is starting to adopt McMurphy's tools of resistance. When McMurphy is in a seemingly powerless position, he laughs at Nurse Ratched, at the other men, and at the situation he is in. Here, Bromden finds himself in a seemingly powerless position. He cannot have what he wants because declaring that he wants it would put him in danger. Whereas this feeling of powerlessness has previously led Bromden to hallucinate fog and to despair about the conditions on the ward, he now cracks a smile at the irony of his situation. This smile is not full-on laughter, but it does hint that Bromden is starting to use laughter and joy as tools to take control of his own experience on the ward.
In Part Three, when the men go on McMurphy's fishing expedition, they have an altercation with some men at a gas station. McMurphy uses dramatic irony and an idiom to intimidate the gas station attendant:
He put his hands up in the guy’s face, real close, turning them over slowly, palm and knuckle. “You ever see a man get his poor old meat-hooks so pitiful chewed up from just throwin’ the bull? Did you, Hank?”
He held those hands in the guy’s face a long time, waiting to see if the guy had anything else to say. The guy looked at the hands, and at me, and back at the hands.
The gas station attendant first doesn't want to help the men because he believes they are patients at the mental hospital. Then, when the doctor lies and says they are not patients but rather a work crew, the attendant begins playing mind games. He tries to offer far more expensive services than the men first requested. He is attempting to intimidate the doctor into admitting that he is a liar. McMurphy responds by posturing as an even more dangerous patient than he really is. He claims that he has killed a man with his bare hands. When the attendant calls his bluff and accuses him of "throwing the bull" (i.e. being all talk and no action), McMurphy shows him his cut-up hands. He lets the man think that the injury came from an act of extreme violence. Bromden and the rest of the men know that McMurphy injured his hands trying to lift the control panel, not killing someone. They are all in on the joke McMurphy is playing on the gas station attendant.
The dramatic irony in this moment is funny. McMurphy plays it not only to intimidate the gas station attendant but also to amuse the other patients. Rarely do they get to have the upper hand in a power exchange. He shows them how even when they are being treated as less-than, they can use humor and inside knowledge to empower themselves. The flip side of this inside joke is that McMurphy shows his nature to the other patients. He is apt to bluff to get his way. As Nurse Ratched eventually points out to the rest of the patients, McMurphy bluffs all the time to win money off the rest of them. McMurphy eventually loses some of the men's trust because of his bluffing, but eventually he goes down in everyone's book as the martyr who taught them how to get power within a system that tries to keep them down.