The Greendale study group reunites; Jeff butts heads with the new biology teacher; Dean Pelton finds a new nemesis in the dean of the Air Conditioning Repair Annex.

Chang gets used to his new job; Britta reacts to a friend being taken hostage in a foreign country; Annie asks the group to help bring down her new friend; Professor Cligoris struggles to behave appropriately.

The study group struggles to incorporate a fellow classmate while working on a project for Professor Kane’s class. Meanwhile, Chang causes a fire while trying to solve a strange mystery of his own making.

When Jeff introduces an element of randomness into Troy and Abed’s housewarming party, reality splits into six timelines in which the group’s complicated relationships play out in different ways.

When Britta finds that an anonymous personality tests suggests that one of them is a homicidal maniac, the study group members use a series of scary Halloween stories to expose the killer.

When a drag queen's song makes Hawthorne Wipes an iconic gay product, Pierce embraces it - until his homophobic dad Cornelius shows up to squelch the idea. Meanwhile, Vice Dean Laybourne recruits Troy for his air conditioning repair school.

The study group helps Annie move in with Troy and Abed - except for Jeff, who lies to get out of it but is busted by dean Pelton.

The dean is given the task of making a Greendale commercial, but the shoot soon goes over budget and spirals out of control - with Abed documenting the experience.

When Shirley agrees to coach Jeff in foosball, they realize that she bullied him mercilessly when they were kids. And after she breaks Abed's limited edition Dark Knight DVD, Annie goes to great lengths to cover up her mistake.

The study group is slowly convinced to fill in for the Glee Club at Greendale’s Christmas pageant after Abed decides he wants them to spend the holiday together.

Pierce comes to Shirley with a business proposal just as she's about to get married to Andre. Meanwhile, Troy and Abed try to act "normal" for the wedding, Britta discovers a new skill, and Jeff struggles with his toast.

The members of the Study Group take jobs as celebrity impersonators to pay off Abed's debt to a celebrity impersonator business, but can Jeff be Ryan Seacrest without his fragile ego spiral out of control?

When Britta falls for the human embodiment of the Subway sandwich chain, Shirley and Pierce hope to use the situation to their advantage.

The students of Greendale are drawn into an epic pillow fight as Troy and Abed start a war that threatens to destroy their unique friendship.

While Britta struggles to stay away from her old carny boyfriend, Jeff becomes obsessed with their relationship. Meanwhile, the dean stops by Troy and Abed's to recruit Troy for the dean of the school of refrigeration.

After sending Troy and Britta on a date, Annie volunteers to keep Abed company in his Dreamatorium. But when she uses the fantasy to try to force Abed to be more empathetic, his personality fractures into dream versions of all of their friends.

When the yam the study group was growing for biology class is killed, Troy and Abed are on the case. Once they pin the crime on Todd, Annie and Jeff team up to argue their case to the class.

After a classmate suddenly dies, the study group decides to host a memorial. But when Jeff turns his speech into an angry anti-Greendale rant, the gathering quickly becomes a riot that is violently suppressed by Chang.

When Abed claims the Dean has been replaced by a doppelgänger he is forced to take psychiatric treatment. Naturally, the rest of the study group joins him at his session with Dr. Heidi.

The study group stages an elaborate heist to break in to Greendale and free Dean Pelton from the clutches of Chang.