The episode begins with the boys--Stan, Kyle, Cartman, and Kenny--at school, where they are discussing the upcoming school play. The play is a rendition of "The Lion King," and the boys are excited about their roles. Stan is particularly enthusiastic about the production, while Cartman is more focused on how he can manipulate the situation to his advantage.

As the boys prepare for the play, they encounter a new character, Mr. Garrison, who is now a woman after undergoing gender reassignment surgery. Mr. Garrison, now Mrs. Garrison, is trying to adjust to her new identity and is determined to be a good teacher. However, her transition leads to confusion among the students, especially when she tries to explain the concept of gender identity.

Meanwhile, the boys are rehearsing their lines for the play. During a rehearsal, Cartman, in his usual fashion, tries to take control of the situation and ends up causing chaos. He insists on changing the script to make it more appealing to him, which frustrates the other boys. They argue about the importance of sticking to the original story, but Cartman is adamant about his changes.

As the play approaches, the boys face various challenges, including their costumes and the need to practice more. Tensions rise as they struggle to work together, with Cartman often undermining the group's efforts. The boys' friendship is tested as they deal with their individual insecurities and the pressure of performing.

In a pivotal moment, the boys discover that they need to address the issue of gender in their play. They decide to incorporate a subplot that reflects the changes happening with Mrs. Garrison. This decision leads to a series of comedic misunderstandings and awkward situations as they try to navigate the complexities of gender identity while still focusing on their performance.

As the day of the play arrives, the boys are nervous but excited. They put on their costumes and prepare to perform in front of the school. The performance begins, and the boys struggle to remember their lines and cues. Cartman's insistence on improvisation leads to a chaotic and humorous rendition of "The Lion King," filled with unexpected twists and turns.

During the performance, Mrs. Garrison's presence becomes a focal point, and the boys' attempts to address gender issues in their play lead to a series of comedic mishaps. The audience reacts with laughter and confusion as the boys navigate their way through the performance, ultimately leading to a chaotic but entertaining conclusion.

As the play wraps up, the boys reflect on their experience and the challenges they faced. They realize that despite their differences and the chaos that ensued, they managed to come together and put on a show. The episode ends with the boys celebrating their performance, highlighting the importance of friendship and teamwork, even in the face of adversity.

In the ending of "Eek, A Penis!", the boys of South Park are faced with the chaos that ensues after a series of misunderstandings regarding a supposed "penis" that has been spotted in the town. The episode culminates in a confrontation where the boys realize the absurdity of their fears and the situation. Ultimately, they come to terms with the ridiculousness of their panic, and the episode ends with a humorous resolution that highlights the boys' friendship and their ability to navigate through bizarre circumstances.

As the episode progresses towards its conclusion, the scene shifts to the boys gathering at the school, where they are discussing the recent events surrounding the mysterious penis sightings. Stan, Kyle, Cartman, and Kenny are all visibly anxious, their expressions a mix of confusion and fear. The atmosphere is charged with tension as they recount the various rumors that have spread throughout South Park, each boy contributing to the escalating hysteria.

In the next scene, the boys decide to take matters into their own hands. They form a plan to confront the supposed threat, which they believe is a monstrous penis that has been terrorizing the town. Their determination is palpable, and they rally together, showcasing their camaraderie despite the absurdity of the situation. The boys' motivations are driven by a mix of bravery and the desire to protect their community, even if the threat is entirely fabricated.

As they venture out into the town, the boys encounter various townsfolk who are also caught up in the panic. The visual chaos of the town is evident, with people running in all directions, shouting about the penis. The boys' interactions with the townspeople reveal their growing frustration and confusion, as they try to make sense of the hysteria that has gripped South Park.

The climax of the episode occurs when the boys finally confront what they believe to be the source of their fears. In a dramatic moment, they come face to face with a large inflatable penis that has been mistaken for a real threat. The absurdity of the situation hits them all at once, and the tension breaks as they realize how ridiculous their fears have been. Laughter erupts among the boys, and they share a moment of relief, recognizing the humor in their panic.

In the final scenes, the boys return to their normal lives, their friendship strengthened by the experience. They reflect on the events with a sense of camaraderie, joking about how they let their imaginations run wild. The episode concludes with a humorous twist, as the inflatable penis is revealed to be part of a local festival, further emphasizing the absurdity of the entire situation.

By the end of the episode, Stan, Kyle, Cartman, and Kenny have all learned to navigate the chaos together, showcasing their resilience and the strength of their friendship. Each character returns to their usual antics, but with a newfound appreciation for the ridiculousness of their fears and the importance of sticking together in the face of absurdity.

In the episode "Eek, A Penis!" from season 12 of South Park, there is no post-credit scene. The episode concludes without any additional content after the credits roll. The focus remains on the main storyline, which revolves around the boys' reactions to a new school policy regarding the use of the word "penis" and the ensuing chaos that follows. The episode wraps up with the resolution of the main plot, leaving no further scenes or jokes after the credits.

In 'Eek, A Penis!', Mr. Garrison undergoes a sex change operation to become Mrs. Garrison, but his penis is later revealed to have developed a mind of its own and escapes, leading to a series of chaotic events.

The boys, particularly Stan and Kyle, are initially confused and disturbed by Mr. Garrison's transformation into Mrs. Garrison, leading to humorous and awkward interactions as they try to process the change.

Mr. Slave, who is Mr. Garrison's former partner, plays a significant role as he helps Mr. Garrison adjust to his new identity and later becomes involved in the chaos surrounding the runaway penis.

The town is thrown into a frenzy as the runaway penis causes havoc, leading to panic and absurd situations, showcasing the town's exaggerated and comedic response to bizarre events.

The penis having a mind of its own serves as a comedic device that explores themes of identity and autonomy, while also providing a satirical take on gender and sexuality, as it interacts with various characters throughout the episode.

"Eek, A Penis!" from South Park's twelfth season is not family-friendly and contains several potentially objectionable elements. Here are some aspects that might be upsetting for children or sensitive viewers:

1. Graphic Humor: The episode features explicit jokes and visual gags related to male anatomy, which may be inappropriate for younger audiences.

2. Sexual Themes: There are discussions and scenarios involving sexual content and innuendos that are not suitable for children.

3. Violence: The episode includes scenes of violence, including characters being harmed in exaggerated and comedic ways.

4. Dark Humor: The show often employs dark humor that can be unsettling, particularly in how it addresses serious topics in a satirical manner.

5. Language: There is the use of profanity and crude language throughout the episode, which may not be appropriate for younger viewers.

These elements contribute to the overall tone of the show, which is known for its irreverent and controversial approach to various subjects.