The World's Largest Rodent is the story of Billy, a troubled teenager trying to navigate through a world dangerously close to insanity. His mother, suffering from a failed suicide attempt, lives in a mental institution in a near catatonic state; his father, by all accounts a total waste, has disappeared entirely from his life. His older sister, Meg, tries to support them by posing for internet fetish photography. His only friends are a teenage lesbian named Chastity whom he desperately lusts after and a large, magical, talking capybara, the world's largest rodent. When Meg decides that Billy needs a father figure and seduces a twenty-year old latin lothario named Reynaldo, Billy swoops into action to save his family. He embarks on a difficult and ill-advised plan to steal his mother from the mental institution. Against all odds, he succeeds, bringing her home to live in his bedroom unbeknownst to the rest of his family. Billy tries everything from disturbing puppet plays to violence to break his mother out of her near coma, but nothing seems to succeed. In desperation, he turns to the creature he seems to have summoned out of his imagination, the unpredictable magic of the capybara. The play enfolds in a series of episodes, some real, some imagined, in a twisted, hilarious satire on faith, the medical system, and family drama. Can Billy succeed in rescuing the mind of his mother? Will the capybara's magic be sufficient? Why is Reynaldo actually from Carbondale, Illinois? Will Meg succeed in her quest to become an internet diva? And will Billy survive a school system determined to crush his spirit?