At South Park Elementary, Butters Stotch discusses the Arnold Schwarzenegger sex scandal, confusing it for a Terminator movie. Stan Marsh and Kyle Broflovski correct Butters, but he misunderstands everything the two boys say. An incensed Cartman enters the cafeteria in a screaming rage and threatening to kill everybody as he rants about the results of the students' annual school physicals, claiming that teachers have posted a list of all the boys' penis sizes in the hall for everyone to see. Believing the results to be inaccurate (especially since he is at the bottom of the list), he measures every boy's penis and posts his own findings in the hall. He is soon called to Principal Victoria's office, where he learns that the first list actually showed how much every student had grown in height since the previous year's physical. Principal Victoria berates him for always taking situations the wrong way and for not thinking straight. To make matters worse, Cartman has found that his penis really is the smallest of all the boys in the school, which ends up infurating him. At a consultation session with a psychiatrist, Cartman is tested to see how he deals with anger. Initially, he shows no emotion during the session when the psychiatrist tries to incite him into anger with a series of fat jokes and insults. However, during this time, in a sadistic, yet silent manner, Cartman discreetly uses an iPhone to send fake chat logs and a fake police report that indicate the psychiatrist was involved in an affair with a 14-year-old over the internet. The psychiatrist's wife is notified, calling her husband before committing suicide over the phone. Cartman coldly tells the horrified psychiatrist his infamous catchphrase, "I'm not fat. I'm big-boned".
Soon after, Cartman is sent to an anger management class along with a member of the Tea Party, a wigger, Wayne D, a Marine, Tuong Lu Kim, Michael and several others. It soon becomes apparent that every person in the class has issues with their penis size. Meanwhile, Randy Marsh gives a talk to the fourth grade class about human sexual behavior and presents a ridiculously complicated formula for calculating "adjusted penis size," or "T.M.I." which is simply a way for him to say he is above average, even saying so as an example in front of the class. Soon afterward, the Surgeon General of the United States presents her own talk to correct Randy's inaccurate information, giving her own bizarre formula that prompts Randy to beat her up in front of the class and ending up at anger management as well. Randy and Cartman incite the group to riot against the federal government.
They take over a Federal Express shipping center, mistakenly believing it to be a government office (though he pretends he knows that after being told), Randy names their group the "Pissed off and Angry Party" and presents their demands to a national television audience; the resignation of the Surgeon General, Obama's birth certificate, "mom's to stop trippin'", and to "fuck Kyle". The movement spreads around the country, with other FedEx locations being taken over. Even Butters joins in when he realizes that his T.M.I. is not as high as he thought according to the Surgeon General's new T.M.I. formula. In response, Cartman's psychiatrist develops a theory that the true source of everyone's anger is their embarrassment over their small penis sizes. After he informs the Surgeon General, she addresses the nation on TV. She says that although her formula for calculating T.M.I. is accurate, the national "average" value has been re-defined downward to 1.5 inches. The violent movement instantly breaks up, since every man involved now falls into the "above average" range - except for Cartman, whose penis is so small that it falls below even the new national average (as his penis size is 1.4 inches). Cartman's frustrated remarks are dismissed by the Pissed off and Angry Party's former members as they proclaim that "America is back!"
AV Club gave "T.M.I" a "A-" rating saying: "So far, this season has been pretty heavy on the straight-up satire, with plotlines built around very specific targets (the cult of Apple, The Comedy Awards, the royal wedding). But “T.M.I.” breaks that stride, both keeping things on a smaller scale and widening the scope of the show's mockery. Unlike some of the weirder tangents of late, it’s a more modest story about Cartman and eventually Randy losing their shit, a dream-team combination of two of my favorite standard plotlines. And rather than zeroing in on someone or something in particular, it makes fun of something far more universal—namely the fact that so many people have become so pissed off (and loud) lately, without really being able to articulate why."
IGN gave "T.M.I" a "8.0" rating saying: "There are many great moments in this story, and that's what sets it apart from its predecessors this season. I felt like the other episodes were a long string of hit or miss (mostly miss) gags with no real direction, but the jokes here are wonderfully done, and they all tie into a theme that gradually builds. I actually enjoyed the episode more during a second viewing, because knowing the "point" of the story gives Cartman's initial rampage in the lunchroom more context."