At Tegridy Farms, Randy struggles to cope with other South Park citizens growing their own weed at home, and after being "insulted" by Towelie, starts coming to terms with the fact that he might be a towel. Meanwhile, Cartman decides to pull a prank on Kyle by having the US ICE (Immigration and Customs Enforcement) team detain his family at a detention centre alongside several Mexican immigrant kids.
The episode begins with Randy Marsh singing his own version of the South Park theme song while promoting his business, Tegridy Farms. Then Randy leads several people through a guided tour of his weed fields, tourist areas, and gift shops.
Afterwards, in the Marsh's living room, Cartman lays on the couch, lamenting over the changes he thinks have happened since the Marsh's moved to the farm and the problems his generation faces. Stan, typing away at his laptop, seems to ignore him. Randy enters a short time later and asks his son if he is finished entering all the weed orders, and is surprised to learn that sales are down again. Stan explains that people aren't ordering as much as they did the previous month, with Randy asking, "what the hell is going on?"
Randy pays a visit to Stephen Stotch, delivering his regular order of weed to him personally. Stephen then declines, and when Randy asks if he was "getting all sober on him", he shows him to his backyard, proudly displaying his personal marijuana plants he started growing. Randy gets angry, claiming that Stephen stole his idea of growing marijuana while Stephen defends himself by saying that anyone can grow weed in their yard.
During the argument, Mr. Mackey walks in, looking to pick up the seeds that Stephen was going to give him, so that he could try growing his own weed at home too. This makes Randy even more upset, exclaiming "Fuck you guys!", and that he was going to get revenge on Stephen for messing with his Tegridy.
Cartman walks down the aisle of a convenience store, mixing several different kinds of soda in a cup along with a generous amount of coffee. While paying for his drink at the checkout, the clerk asks him if he's okay, to which Cartman answers, "Kids are being handed a world that's broken and sick. We aren't the ones who messed this planet up, but we're the ones who'll pay the price". The clerk stares at him oddly and then wishes him a good day. Walking out of the store, he sees two US Immigration vehicles race down the street, sirens flashing.
The US Immigration officers are stopped in front of the Stotch residence, escorting Diego, Stephen's gardener, out of the house on the grounds that he is an illegal immigrant. Cartman, watching in amusement, asks one of the officers what's going on, and is told that someone had called in an anonymous tip that there was a possible illegal alien working for the Stotchs. Diego's wife and kids show up and start protesting his arrest. The officers respond by separating the kids from the adults, and Diego from his wife, and placing them in separate cars, telling them that they are being taken to "detention centres".
Stephen, angry and frustrated that his gardener was seemingly arrested for no reason, asks the ICE agents if it was Randy Marsh that gave them the tip. He's told that if Diego 's family checks out, they'll be released. Cartman, standing beside the officer, is surprised, saying "Detention centers? This is nice! When did we start doing this?" and asks if anyone can call in and make an anonymous tip to have the immigration officers come to their house and take them away.
Kyle, sitting at home on the couch eating cereal and watching Russell Crowe Fightin' Around The World on TV, while Ike plays with blocks on the floor, gets a phone call. Cartman is on the other end, asking him if he remembers calling him a butthole at school in front of Susie Tobbler. Kyle responds by saying "Yeah, because you were going to snap her bra". Cartman then asks him to apologise to him for every time that he was a dick to him. Kyle scoffs and Cartman responds by asking him "Are you sure you won't take that back? Ok Kyle, just remember, I gave you a chance".
Almost immediately afterwards, Kyle's doorbell rings. Ike runs to open the door, and four US Immigration agents burst in, quickly spreading out and rounding up Gerald, Sheila, and the two kids together in the living room. Gerald protests loudly, saying that they are American citizens, and that the officers can "get the fuck out of my house!"
The officers escort the four Broflovskis out of their house and towards their cars, again separating them. Cartman watches from across the street in his bedroom, using a pair of binoculars, eating Cheesy Poofs, and giggling to himself over the situation he caused. Kyle, after being placed in one of the cars, notices Cartman watching the events unfold, and Cartman waves at him from his bedroom window. The cars then clear off.
In the courthouse, in front of a town jury that includes the mayor of South Park, Stan Marsh pleads his father's case, stating "no more home-grown marijuana", while Randy, the only other person there along with Towelie, cheers him on, pretending to be the voices of a crowd. Stan, just as confused as the jury, reads increasingly silly statements about the dangers of growing weed at home, and states that weed should only be grown with Tegridy.
A little while later, in the car on the way home, Randy vents over the government's decision to let people continue to grow weed in their yards. He tells both Stan and Towelie that he's done with South Park and that Tegridy Farms is all that matters to him now.
A US ICE bus pulls up to one of their detention centers and stops, letting a few dozen children out into the yard. All of them appear to be Mexican, except for Kyle. An older man in a striped shirt named Jeff Corrigan greets them along with Dave who is a (terrible) Spanish translator. He acknowledges that the children have been separated from their families, but promises them that there is a lot of "fun" in store for them at the camp.
Jeff hands out a piece of aluminum foil to each child as they walk in, and directs them into a gated room with several sleeping bags laid out across the floor. An officer comes in with a clipboard, asking the children to raise their hand when they hear their name. When the officer calls out "Broflovski" and Kyle tells him that he isn't Spanish, but Jewish, the officers begin to look worried. Jeff, surprised, asks the ICE team how a Jew got rounded up with the Mexicans, and that they have to get him out of there quickly before people start thinking they're racist.
Back at Tegridy Farms, two men pull up in front of Randy's house in a black Cadillac. They walk up to the front porch, meeting Randy and telling him that they represent a billion-dollar marijuana company called MedMen. Randy is at first apprehensive, telling the city-folk that "you can't buy Tegridy", but the two men tell him that they're not there to buy, but there to work with him since they share the common goal of not wanting people to start growing weed at home. Lighting up a joint and passing it around, the trio begin to conspire...
At the detention center, Jeff apologises to Kyle for "their little mistake" and assures him that they will get him home as soon as they can. Kyle asks about the other children held at the camp with him, and is told that these kinds of things must be hard for "his people". Kyle then asks if the ICE is concerned at all about what they're doing to the kids, pulling them away from their families and making them despise the US government. Using a superhero movie as an analogy, he explains that doing what they're doing is, in essence, creating a "Mexican Joker", much like the Joker villain from the Batman movies, and that this Mexican Joker is going to grow up to take revenge and fight back.
The ICE, afraid that what Kyle is saying is true, begin to question him further, asking him who Mexican Joker is, and if Mexican Joker understands that the ICE officers are just trying to their job. Kyle tells them that the Mexican Joker doesn't care about their reasons, only revenge against them. At this point, Jeff asks Kyle to wait outside while he talks with the other two officers in his office.
Jeff tries to come up with a way to find out who the Mexican Joker is, with one of the other officers suggesting that they may interrogate the children. Jeff waves this off and after some more thinking, comes to the conclusion that Kyle is actually on the Mexican Joker's side, staring at him through the window.
Randy sits at the laptop in his living room, joint in one hand and typing furiously with the other. Towelie walks in shortly after and is in disbelief that Randy, after fighting to keep Tegridy Farms independent for so long, has decided to make a deal with the two men from the billion-dollar marijuana company, MedMen. Randy says that he's been working on a merger between Tegridy Farms and MedMen with the goal of stopping home-grown weed operations. Towelie, saddened by the news, reminds Randy that he once said that weed should be for everybody, not controlled by one company. Randy gets upset and tells him that he is the president of the company, and Towelie is just a towel. Towelie fires back by calling Randy a towel, and explains that "weed is a gift from God, and that it shouldn't be exploited by a stupid towel". Randy yells back, "I am NOT a towel!"
Jeff attempts to put on a puppet show for the children, trying to make their experience less frightening. The puppet show features Princess Star and the Mexican Joker and tries to teach them forgiveness. Inadvertently, however, Jeff ends up traumatising the children further by enacting a scene where Mexican Joker is raping the princess. Thankfully, this doesn't go on much longer as another officer calls out to inform Jeff that another bus-load of suspected immigrant children have arrived.
In this group of children is Eric Cartman. After being walked inside the camp, Cartman approaches Kyle, to which Kyle reacts with a surprised and angry, "What the fuck are you doing here?" Cartman explains that Jimmy pissed him off earlier by telling the teacher that he was texting in class. Cartman then threatened to have him taken away to a migrant detention center and states that he had already done this to Kyle. Stan, overhearing the conversation, then has Eric sent to a migrant detention center in an ironic twist of fate.
Kyle, extremely upset, says that he hasn't seen his parents in two weeks and that no one even knows where Ike is. Cartman mentions that what's important right now is that they're trapped there together. He tries to rally all the other children by singing "It's the Hard Knock Life", but fails.
Walking down the street, Randy comes across a cotton product store with a towel display at the front. After being asked by the store clerk if he was going to buy something or stare at towels all day long, Randy yells, "I'm not a towel!" back at him while turning around and walking back up the street. He slowly starts becoming more and more frustrated with the home-growers, hearing Stephen's, Mr. Mackey's, and Jimbo's voices in his head, mocking him. After battling with towel-related hallucinations, he falls to his knees in the middle of the street, moaning.
A Mexican child lies atop a table at the detention center, connected to a machine via cables, and is being electrocuted by the ICE. When Jeff bursts into the room and asks them what they're doing, the officers claim that they heard that electroshock therapy sometimes aids people getting over traumatic experiences and that if they apply this "treatment" to all of the children, they would help the Mexican Joker overcome his traumatic experience. Jeff asks them if they are both crazy, and tells them that they can't possibly shock every child held at the camp due to "budget restrictions". After some more arguing over how to determine which child is the nonexistent Mexican Joker, Jeff decides it's time to involve the military.
During the middle of the night, Kyle lays awake in the camp. Cartman sits up beside him, still singing lyrics from "It's the Hard Knock Life", and starts to wake up some of the other children. Kyle, exhausted and frustrated, drags his aluminum foil blanket over to the nearby wall and sits down, wrapped up in it. Cartman walks over and starts telling him to lighten up, saying how awesome it is that you can have people rounded up and sent to detention camps before realising that because of Kyle's Jewish background, he is "super-sensitive to this stuff" and that it "wasn't so sweet" that he had him taken to a detention camp. While he is apologising semi-sincerely, Kyle comes up with an idea that will get all of them out of the camp, asking Cartman to bring him all of the aluminum foil the kids were given and a pair of scissors.
It's night-time in South Park, and Jack and his wife are washing their dishes after dinner. They decide to harvest some of their home-grown weed and get stoned that night. As Jack opens the sliding door and steps out into the backyard, a rustling sound is heard from behind his marijuana plants, and a shadowy figure slips away. He calls out to see if anyone is there, and after a brief silence, heads out into his garden. His wife comes to the door to check on him and as he turns around to ask her how much weed she wants, both Jack and his garden explode, leaving blood, entrails, and marijuana leaves all over the lawn and his wife.
All over town, people's backyard cannabis gardens start to explode, one by one. The news begins to report this as a "brutal act of terror", and that the FBI believe they know who is responsible: Mexican Joker. The newscaster speaks with Commander Miller of National Defense, who states that Mexican Joker has no compassion, no understanding, and that he just wants to invoke fear. After advising everyone to stay inside, Miller expands on his Joker theory, stating that whatever made the Mexican Joker this way must have been traumatic, and happened a long, long time ago...
... except it didn't, and instead of a flashback we see present-day Jeff and the two ICE officers who believe that they're experiencing a flashback, run out of the office and down the hall to check on the children. As they come up to the gate, they see Kyle and Cartman sitting at the front of the room, with Kyle reciting Hebrew passages. Jeff then exclaims that Kyle has converted all of the Mexican children to Judaism, with them proving his point by repeating the Hebrew passage back to Kyle. They have also turned their aluminum foil sheets into imitation yarmulkes (traditional Jewish hats). Now that all of the children in the camp are effectively Jewish, one of the ICE officers points out that now they will have to let them all go free, and that this is how Mexican Joker escapes into the public. Jeff reacts but pulling out his pistol and killing both of his comrades, then shoots the guard behind the gate to the children's room. Kyle and Cartman stand surprised, while Jeff fumbles for his keys and mutters that he helped the Mexican Joker escape and that the Mexican Joker should remember that.
Kyle, still amazed at the stupidity of the ICE, yells at Jeff that there is, in fact, no Mexican Joker, and tries to explain that what he said before was just an analogy and that all people make their own choices to shape their futures. Jeff, staring at Kyle for a few seconds, suddenly blurts out, "I must be in the wrong flashback", and runs away down the hall, keys in hand, and shortly afterward a car door is heard slamming shut and then the sound of screeching rubber as Jeff drives away.
At the dinner table in the Marsh house on Tegridy Farms, Randy puffs on a joint before sitting down with his family, pointing out that Tegridy is finally turning a profit again, and that they're on their way to becoming the biggest weed brand in the country. Still being ignored by his family, Randy pushes them to call him a towel again, like Towelie did earlier, saying that he won't be pushed around anymore, and Sharon, finally humouring him, calls him a towel before standing up abruptly and walking away from the table. Randy then smirks and yells, "Best towel you've ever had, bitch!"
AV Club gave "Mexican Joker" a "C+" rating saying: "Mexican Joker has some good gags, and gets in some solid shots at the horror of Trump’s immigration policies, as well as the naked opportunism of Big Tobacco supporting the flavored vape ban. That being said, the episode ultimately tries to do too much at once, and feels awkward and disjointed. In previous serialized seasons, the show eased its way into each thread, often introducing them one episode at a time before resolving them all during the final stretch."