One day at School, Mr. Mackey has called Ms. Cartman and Cartman to his office to discuss the latter's behavior. Liane bursts into tears after explaining how difficult it is to control her son's behavior. Mr. Mackey recommends a TV show called Nanny 911, which features Deborah Carroll, Yvonne Finnerty, and Stella Reid.
At his house, Cartman is playing on his Xbox 360 when Nanny Stella arrives with her camera crew. She promptly annoys Cartman by taking away his Xbox, so he gets revenge by manipulating her to leave, asking her why she didn't have kids of her own, and going as far as even by spitting on her mouth when she tries to speak with him. He goes on to tell her, that it's because she is ugly and she's too old to have kids of her own. Horrified and disgusted by his words, she marches out.
Supernanny also fails to "fix" Cartman, with her ending up in a mental institute feeding on her own feces. Liane asks the doctor treating Supernanny what else she can do, and he recommends another show, The Dog Whisperer.
When Cesar Millan turns up, he instantly makes an impact on Cartman. He treats Cartman like a dog, constantly nipping at his neck, taking him on a walk, leashed, and explaining how he is to be dominated. Cartman is angered so much that he runs away from home. Despite Liane's initial worry, Cesar assures her that he'll return.
He returns and is angered to see Cesar Milan is still there. Cartman threatens to call Child Protective Services, but Liane finally decides to be dominant, causing her son to be submissive. Cartman begins behaving appropriately soon after, and realizes he's changing for the worse (as he sees it). He devises a plan to commit matricide, but Stan, Kyle, Kenny, and Butters refuse to help.
That night, Cartman prepares to go ahead with his plan, but suffers a strange reemergence of his heavily repressed conscience, which convinces him the changes are for the best. He soon vomits out black fluid, which could be the evil within him, and fights his two sides until he passes out.
The next morning when Liane comes down to breakfast, Cartman is going over his homework and eating a healthy meal. Cesar pays a final visit, and Liane asks him if he wants to see Madame Butterfly with her, but he explains she is just a client, and he has other work to be done. Liane is disheartened and invites Cartman, (as if her son was previously her friend) promising to buy him a Mega Ranger if he goes. He asks if he could have two, which Liane agrees to, telling him that he can have whatever he wants. This incident culminated in Cartman returning to his "normal" self, with a sinister look.