"Eek, a Penis!" is the fifth episode of Season Twelve, and the 172th overall episode of South Park. It aired on April 9, 2008.
While Ms. Garrison is off trying to find a way to become the man he was always intended to be, Cartman is put in charge of the classroom.
The episode starts with Mrs. Garrison realizing that "she" is, in reality, still a man. After breaking a window, tipping over a cabinet and kicking her desk, she is taken out of the class by Principal Victoria and Mr. Mackey, who inform her that she should not teach until she gets her personal life in order. Mrs. Garrison reacts angrily and walks off.
Principal Victoria then informs the the students that Mrs. Garrison will, temporarily, not be teaching. She then asks if anyone would like to lead the class, in order to review for a quiz the students will be taking tomorrow. Cartman raises his hand, causing Principal Victoria to try and coax another student into raising his or her hand. After getting no response, she reluctantly agrees to let Cartman lead the class. Cartman then grabs a pointer and demands respect. He then whips the points and calls Clyde to the front of the classroom. He is heard mumbling "Yeah. You're gonna take it Clyde."
Meanwhile, Mrs. Garrison is seen crying on her couch. A news report on protest caused by the Vacanti mouse. Mrs. Garrison then travels to Research Group Laboratories, where the Vacanti mouse was created. She asks one of the scientists if they could possibly grow a penis on a mouse by using some of "her" DNA. The scientist later agrees after Mrs. Garrison tells him she will give them all of "her" money.
Cartman is then seen in Principal Victoria's office, along with two men from the Denver county school board. Cartman mistakenly assumes he is in trouble, so he quickly places blame on the the students' intelligence. Principal Victoria explains to him that he is not in trouble. The two men from the Denver county school board are, in fact, there to ask for his assistance in teaching inner-city kids. He agrees, but only after learning the amount of money that they will pay him. Cartman is later seen bragging to the rest of the boys about the three hundred dollars he will make from teaching the aforementioned children. While Stan and Kenny are indifferent to Cartman's bragging, Kyle becomes irritated. As a result, it is revealed that Cartman does not have "awesome teaching skills" and the only reason the students scored high on their test was due to Kenny propositioning that they take the answers out of the teacher's desk. Kyle then tells Cartman that the inner city kids will "fucking murder" him.
After realizing Kyle was correct, he shaves the middle of his head and creates a comb over, in order to look Hispanic. The scene then switches to the start of the day at Jim Davis High School. A teacher named Mrs. Miller later attempts to get the student's attention, and after much coaxing, succeeds. Mrs. Miller then explains that "Eric Cartminez" will be teaching them.
After a short introduction, "Eric Cartminez" reveals that he will be teaching the students Calculus, much to the students' confusion.
Mrs. Garrison is seen again at Research Group Laboratories, examining the progress on "her" developing penis. "Her" penis, attached to a mouse, later escapes after she attempts to feel it. It runs outside after another scientist opens the exit to the laboratory. Mrs. Garrison then begins to try and catch her penis.
After handing out syllabuses, Cartman then proceeds to tell the students that he is there in order to help them get into college, much to the students' angry disbelief. Cartman then tells the students the reason they think they cannot get into college is because they have not been taught how to cheat properly. He proclaims it is the way white people get ahead, citing Bill Belichick as an example.
Mrs. Garrison is then shown asking Stan, Kyle, Kenny, and Butters if they have seen his penis, much to the boys' confusion. Linda Stotch is then seen washing dishes. She later notices "a penis" running around her house. She informs Stephen Stotch, who proclaims "It's just a little penis." Butters, remembering his aforementioned conversation with Mrs. Garrison, tells his father that the penis must be "his teacher's penis". Stephen then angrily asks Butters how he knows what his teacher's penis looks like, much to Butters' confusion.
Cartman then proceeds to tell his students that, despite being caught taping the other teams' defense, Bill Belichick was able to get away with it after claiming he "misinterpreted the rules". A former student who left the class then rejoins, saying that he thought he should give cheating a try. Cartman then has then the students repeat "I misinterpreted the rules.", and after a few repetitions, they happily proclaim it.
Mrs. Garrison is then seen confronting Stephen about letting her penis go instead of calling her. She then hears a woman scream "Eeek, Eek!" Realizing this may be a sign that her penis may be in the area, asks the woman if she saw a penis. However, after hearing another woman scream, Mrs. Garrison runs off before she can answer her. She chases her penis inside a "Komfort Inn". The penis then proceeds to run into a sauna. She then mistakenly grabs a man's penis after mistaking it for his own, likely due to the steam in the sauna. The man then punches her. She once again notices her penis and begins chasing it.
Cartman is seen reading the answers to his students. A student named Juanita then runs out of the classroom tearfully proclaiming "What's the point to any of this?!" After Cartman tracks her down, she reveals that she will not be attending college due to her pregnancy. Cartman then tells her that they will go and get her an abortion. She tells Cartman that she cannot due to her religion. However, after explaining to her that getting an abortion is "the ultimate form of cheating", she agrees to get an abortion.
Meanwhile, Mrs. Garrison is seen reporting "her" missing penis to the police. Shortly afterwards, Harrison Yates is told a penis was seen at an Italian restaurant. After they arrive at the restaurant, a brief chase begins, resulting in Mrs. Garrison losing her penis down a storm drain.
Mrs. Miller is seen telling Cartman's students that their grades drastically improved, to the point that they will be taking an exam for college credit. She then reveals the exam is heavily monitored to prevent cheating. After an angry confrontation, Cartman reveals that Bill Belichick attempted to win the Superbowl without cheating, and as a result, lost. He then begins to teach the kids how to make cheat sheets and labels for bottles of water.
Mrs. Garrison is seen sobbing on a bench saying that all her money is gone as well as her penis. Her penis then appears, and allows itself to be caught. Later, Mrs. Miller is shown revealing to Jim Davis High School's populace that Cartman's students all scored one hundred percent on their exams. The students then present a plaque to "Mr. Cartminez" for showing them the "white people method". Cartman then joins the students on stage and happily exclaims "I reached these keeeds (kids)".
Later, Principal Victoria is seen telling South Park Elementary's faculty that Mr. Garrison will be returning, as he was able to successfully "become" a man again. Mr. Garrison then proclaims that he was a man all along, and the true difference in gender in the ability to get pregnant. After another teacher objects to this, saying that his wife cannot get pregnant due to her formerly having ovarian cancer, Mr. Garrison exclaims "Well then get an AIDS test, Thomson, 'cause your wife's a dude, faggot... Yeah! I'm back!" whilst jumping in the air.