"Fat Butt and Pancake Head" is the fifth episode of Season Seven, and the 101st overall episode of South Park. It aired on April 16, 2003.
One of Cartman's body parts becomes too famous for its own good. The real Jennifer Lopez is enraged to learn that a new "Diva" has stolen her record deal and her boyfriend. South Park will never be the same after Jenny & Ben Affleck meet the new "Ms. Lopez."
South Park Elementary School is holding a cultural diversity day. Kyle gives a report on the role of Latinos in American technology. A board of Latino community leaders (who are the judges) seem pleased with Kyle's report, then Cartman goes on stage to report on the effect of Latino culture on the arts in America. He says he has a special guest, Jennifer Lopez. However, Jennifer Lopez does not show up, and Cartman merely does a ventriloquist act with his hand acting as the head of "Ms. Lopez". The racism of Cartman's report is quite obvious and upfront. His "Ms. Lopez" hand puppet has a heavily caricatured Mexican accent and constantly talks about eating tacos and burritos which are Mexican dishes despite the fact that Jennifer Lopez is Puerto Rican. "Ms. Lopez" is also nearly incapable of pronouncing the "J" in her name (which Cartman tries to correct unsuccessfully). Despite this, the board of Hispanics give him first place for having the best report, and he wins a $20 gift certificate at the mall. This angers Kyle, as he thinks Cartman's speech is racist and immature, and because while Kyle labored over his speech, it is implied that Cartman spent very little time in preparation.
Cartman further enrages Kyle by insisting that his hand has a mind of its own. When the children go to the mall, Cartman -- at the apparent behest of Ms. Lopez -- uses his gift certificate to record a music video (in which Ms. Lopez sings of her love of tacos and burritos, and of giving "taco-flavored kisses"). The video gets sent to the record company representing the real Jennifer Lopez. The executives decide to replace the more difficult human performer with the puppet because they cannot have two Jennifer Lopezes. When the real Jennifer Lopez learns she's being fired, she gets angry (all throughout the episode she is shown as extremely mean and swears at random people). Jennifer Lopez and her husband-to-be, Ben Affleck, show up at South Park Elementary. Jennifer starts to beat up Cartman until he pleads that he'll stop his Ms. Lopez ventriloquist act. As the two celebrities leave, Ben catches sight of (Cartman's hand) Ms. Lopez. He immediately falls in love with her.
Cartman begins to become insane due to the tension between Lopez and Cartman fighting for control of her actions. He starts to suffer from insomnia because Ms. Lopez forces him to stay up all night (she is writing and recording songs for her album). When not working with her music, Ms. Lopez becomes involved in an increasingly romantic relationship with Ben Affleck. Cartman hates the relationship; he doesn't like Ben Affleck. After waking up one morning to discover Ben naked in his bed (Ben apparently had sex with Ms. Lopez), Cartman learns that Ms. Lopez and Ben are planning to get married.
The news of the wedding angers the real Jennifer Lopez. During the ensuing frenzy, Cartman decides to make a run for it. At a bridge, Jennifer Lopez, the police, Ben Affleck, the people from the recording company, Kyle, Kenny and Stan catch up with Cartman and Ms. Lopez. Everyone (except the boys) starts to argue about Ms. Lopez. Ms. Lopez screams for everyone to be quiet. She then makes the confession that she is not Jennifer Lopez, but Mitch Conner, a con man who has been moving around from town to town. His voice is different from Ms. Lopez's, as well as identical to Cartman's, and he has no hair, unlike Ms. Lopez. He apologizes to Ben for playing around with his love and states that he will die, as he has recently consumed a cyanide pill. The last thing Mitch does is look at the sunset and wonder if he will dream. He then "dies", and everyone goes away except for the boys. Kyle asks who Mitch Connor is. Cartman says, "Look, I don't care what you guys believe. But with all the crazy stuff that goes on in this town, isn't it possible, just possible, that something' I don't understand happened here?" When Kyle admits that he believes it's possible, Cartman starts screaming, "Ha ha ha ha haa haa! I got you kind of!" Even though he mocked Kyle that day, Cartman realizes that maybe he doesn't have to impersonate celebrities to feel important.
The episode ends with Jennifer Lopez working at a La Taco restaurant. She complains she had several platinum records and starred in several Hollywood movies. The Mexican next to her is her only sympathizer, saying that he had too. On the season 7 DVD Stone and Parker mention that although its never stated the fellow worker is supposed to be Interscope A&R Gerardo Mejía of "Rico Suave" fame.