Definition of Irony
When Lee Chong's car breaks down on the way to collect frogs for Doc, Gay runs off to find a replacement part and never returns. While Mack and the boys wonder when Gay will return, the fact that he will not return is revealed to the reader in a moment of dramatic irony:
Oh, the infinity of possibility! How could it happen that the car that picked up Gay broke down before it got into Monterey? If Gay had not been a mechanic, he would not have fixed the car. If he had not fixed it the owner wouldn’t have taken him to Jimmy Brucia’s for a drink. And why was it Jimmy’s birthday? Out of all the possibilities in the world—the millions of them—only events occurred that lead to the Salinas jail.... unrelated, irrelevant details and yet all running in one direction.
Mack and his friends' quest to throw a party for Doc is not just an important plot point in Cannery Row—it's also an allegory embedded within the story. The first party goes awry when the gang throws it at Doc's lab before he even gets home, leaving him with nothing but a mess by the time he gets home. The mishap is marked by this moment of situational irony:
Unlock with LitCharts A+Through the broken end of the packing case a frog hopped and sat feeling the air for danger and then another joined him. They could smell the fine damp cool air coming in the door and in through the broken windows. One of them sat on the fallen card which said “Welcome Home, Doc.” And then the two hopped timidly toward the door.
In Chapter 25, the narrator remarks that the Cannery Row community feels a sense of impending doom, their reaction to which is introduced with this instance of situational irony:
Unlock with LitCharts A+It’s all right not to believe in luck and omens. Nobody believes in them. But it doesn’t do any good to take chances with them and no one takes chances. Cannery Row, like every place else, is not superstitious but will not walk under a ladder or open an umbrella in the house.
After Gay does not return from his quest to get a replacement part for Lee Chong's Ford, it is revealed that a chaotic chain of events landed him in jail in Salinas. His jailbreak to attend Doc's party in Chapter 27 is an example of situational irony:
Unlock with LitCharts A+Gay heard about the party clear over in the Salinas jail and he made a deal with the sheriff to get off that night and borrowed two dollars from him for a round trip bus ticket. Gay had been very nice to the sheriff who wasn’t a man to forget it, particularly because election was coming up and Gay could, or said he could, swing quite a few votes.