The episode begins at the start of the school day. Eric Cartman, for some reason, is trying to hang out with and compliment Token Black. Apparently, this happens often as Stan Marsh, Kyle Broflovski, and Kenny McCormick watch dumbfounded. As the conversation ends, Cartman furthers his troubles by asking Token for a fist bump, which Token reluctantly gives.
At the guidance office, Mr. Mackey gives Cartman a lecture and tries to stop this "feud" between Cartman and Token. Cartman tells him that something that happened a long time ago is pissing Token off and that he blames Cartman. Mr. Mackey eventually is able to talk Cartman into dropping it.
In his dream, he voices everyone. He takes the role of Gerry, from World War Z. He has a wife and two daughters. As they eat breakfast, CNN reports on the acquittal of the Trayvon Martin case. Gerry and his wife proceed to take their kids to school.
Later, they realize that they are in a ton of traffic and turn on the radio to see what's up. After listening to "It's a Beautiful Day", they find out that there are race riots because of the acquittal of George Zimmerman. Suddenly, black people start attacking everyone and go after Gerry and co. Gerry and his family bail and climb up a building only to have the black people climb up as well. They encounter Token on the rooftops and he lunges at Gerry.
Cartman awakes from his terrible nightmare.
The next day, Cartman, sleep-deprived, tries to be nice to Token once more. This time, however, Token hurries away.
In class, once again, Cartman is having a nightmare, screaming Token's name.
This leads him back to Mr. Mackey, who is angrier that this "feud" didn't end. Token is called in so that Cartman can tell him what he needs to tell him. Cartman tells Token that he was not in the jury and while Token wonders what he's talking about, Cartman reads him a poem. This poem, entitled "I Was Not the Bullet", basically tells Token that Cartman is innocent.
At a school assembly, after the cheerleaders cheer, while Butters Stotch beatboxes, Cartman raps a different form of "I Was Not the Bullet". This enrages Token and Token goes off on Cartman. This makes Cartman believe the apocalypse has started and he runs home. He grabs his handgun, and dresses like Brad Pitt in World War Z. He then warns everyone on his street. He stops a woman driving a Tesla and makes her drive him to the airport.
At the airport, Cartman runs onto a plane, hurrying people inside, and then tells the pilot to take off.
At a control tower, workers are trying to figure out why a plane took off without permission. One worker alerts his boss of a "survival guide" made by Cartman depicting the apocalypse, sending everyone into a panic.
Cartman explains that an outbreak has started and that they need to go to Iceland. Realizing the plane wouldn't make it, Cartman goes to the bathroom to think. He finds a black man in there. Scared, he blocks the door. He tells everyone that "one of them" is in the bathroom. One passenger, scared to become a zombie, opens the emergency exit and flies out. Now everyone is holding on for dear life. The black man gets out of the bathroom and a flight attendant tries to shoot him. The black man ducks, causing the bullet to bounce around, eventually hitting the ceiling of the plane, causing an explosion.
The only survivors are Cartman, the Tesla driver, and the pilot, although fatally injured. The tesla driver calls her husband to find out nothing is going on even though it's the end of the world. She passes this news to Cartman, giving him hope. The pilot asks Cartman to end the apocalypse and then he dies.
Later, at the Stotch residence, Butters is watching the news. He recognizes Token, patient zero, almost immediately.
At Jimbo's Guns, Cartman attempts to buy a gun. He is informed on the "stand your ground" laws. Distraught, that he can't kill Token, he decides to kill the other patient zero, George Zimmerman.
Cartman and the Tesla driver rush onto another airplane and inform the passengers of the situation. Cartman notices a black man on board and ends up causing the plane to crash.
That night, in Florida, Cartman and the Tesla driver get ready to take out George Zimmerman. The Tesla driver thanks Cartman for everything he's doing and then gets hit by a truck.
The next day, at the Zimmerman residence, George Zimmerman's morning goes just like Gerry's from Cartman's dream. Two agents show up and ask George to kill another African American kid for the sake of the country. George suddenly feels something is wrong and notices Cartman, now in blackface and wearing a dark hoodie, George immediately shoots Cartman. At first, the agents commend him but once they realize Cartman is white, they send him to court.
The Judge finds him guilty and he is executed.
Channel 4 News reports on Cartman and George Zimmerman and how the apocalypse is over. At one of the boys' house, they are watching this report when Token leaves. Cartman gets his attention and spray paints a red circle around himself. After some arguing, Cartman offers a fist bump. Token goes to bump his fist when Cartman shoots him. He says that Token was on his land.
Later, Cartman is dreaming again, and Gerry is saying he loves his family on a boat, heading to the shore.
Cartman wakes up in class because the ending to World War Z was so bad. Kyle points out that the ending shouldn't be what's bothering him. What should be bothering him is the fact that he's a murderer. Cartman is then called to the guidance office.
Mr. Mackey makes Token and Cartman apologize. Token gets mad and goes on a rant about why "stand your ground" laws don't effect white people. This freaks Cartman out and he runs home to start everything over again.
Later, a plane is falling out of the sky.
AV Club.com gave "World War Zimmerman" a "A-" rating saying: "It’s not a perfect episode. The World War Z thing bugs me. It doesn’t have the same lasting power as, say, using World War II-era Looney Tunes to mock Osama bin Laden in "Osama bin Laden Has Farty Pants." And some of the jokes that drive home the more serious points—like Zimmerman's quick receipt of justice once he shoots a white kid—lack the subtlety of the episode's best moments. But these quibbles are minor. There are moments that are as sharp as anything the show has done and even the throwaway jokes are pretty great."
IGN gave "World War Zimmerman" a "8.7" rating saying: "Delicately treading a fine line between hilarious and heinous, "World War Zimmerman" was a return to form for South Park, as it handily lampooned both the Trayvon Martin case and World War Z in one fell swoop."