As the Greendale year-end paintball extravaganza continues, the game takes a dramatic turn with new intruders arriving on the scene. The study group battles it out on various fronts and despite their arguments over strategy - they are all in agreement that they must unite to defeat the enemy.

As the Greendale student body enjoys their year-end picnic, Dean Pelton announces plans for a small, quick, safe game of paintball. As the game heats up, alliances are formed - and broken - and friendships are put to the test. When a mysterious and threatening figure emerges on the Greendale campus, it becomes apparent that this is no ordinary game of paintball.

When the Anthropology class assembles for their final exam, Shirley notices a twinge, which quickly escalates into full-blown labor. As Jeff and Britta argue about how best to help, Chang is anxious to claim this "early" labor as clear evidence that it's a "Chang Baby!" Meanwhile, Greendale is hosting a World Food Festival in the parking lot and a riot ensues - Dean Pelton is caught in the crossfire.

As the study group gathers to assemble their 20th and final Anthropology diorama of the year, they begin reminiscing about their favorite times together - including a trip they made to a western ghost town, a last minute glee club performance, the clandestine trysts that Jeff and Britta have pulled off and the cornucopia of costumes that Dean Pelton has managed to wear over the year. Meanwhile, Troy's pet monkey returns, only to disappear back into the school's ventilation system. On the case, Senor Chang quickly dives in to retrieve the monkey - along with all the loot he has stolen.

As everyone settles on their spring semester electives, Troy and Britta explore the fundamentals of acting, while Abed tackles an advanced study of 1980s sitcom "Who's The Boss?" with a professor who has written a book on the topic. Meanwhile, Pierce and Jeff enjoy a wine tasting class, where Pierce meets "Wu Mei" a mysterious Chinese woman who sweeps Pierce off his feet. Suspicious, Jeff vows to find out what'd going on with Wu Mei and why she would agree to marry Pierce so quickly.

Capitalizing on Abed's love of cinema and pop culture, Jeff plans a very special Pulp Fiction style surprise party for Abed's birthday. The tables turn, however, and while the study group awaits their arrival at a restaurant, Abed stages another dinner with an unsuspecting Jeff at another restaurant.

Annie organizes a baby shower for Shirley, while Shirley plots to keep Senor Chang out of her life. Meanwhile, Britta has a mysterious new love interest named Lukka, whose classroom poetry soon reveals a dark past.

As the school prepares for the Vice President's visit, Dean Pelton organizes the first student elections. Annie, who is determined to win, is pitted in a tough battle against Jeff, Leonard and Star Burns. Meanwhile, Abed has noticed the secret service agents casing the school and develops a clandestine friendship with special agent Robin Vohlers.

Pierce ends up in the hospital after ingesting mysterious pills and believes he's dying. The study group gathers at his bedside as he imparts his "final" words of wisdom and shares specially chosen gifts - which are secretly meant to torment them. Britta struggles over what to do with her blank check for "charity," Jeff contemplates the possibility of meeting his long lost dad and Troy meets his idol LeVar Burton.

Troy and Abed compete for the attentions of the college librarian, while Britta strives to be progressive and befriends a fellow female student whom she believes is gay. Meanwhile, Jeff finds himself reluctantly hosting an impromptu party at his apartment when Professor Duncan invites himself over to watch a soccer match.

When Jeff becomes concerned about "Fat Neil," a fellow Greendale student who is a bit of a loner, Abed proposes that they invite him to play a game of Dungeons and Dragons to boost his spirits and his confidence. But when Pierce discovers that he's been excluded, he forces his way into the game and takes charge, disrupting their delicate plan.

When Annie decides to stage a production at a local middle school to spread an important message about staying away from drugs, Pierce becomes overwhelmed with the excitement of performing and decides he needs a bigger role. When his over-the-top behavior threatens to ruin the production, Senor Chang comes to the rescue, earning admiration from the group.

Annie returns from winter break to find that her crush "Rich", the Dr., has enrolled at Greendale Community College, sparking a heated debate about whether to add Rich and/or Senor Chang to the study group. Shirley's ex-husband Andre is back in the picture and Shirley has some big news for everyone.

When Abed wakes up in stop-motion animation, he takes it as a sign that he and the group must re-discover the meaning of Christmas. Meanwhile, Jeff and Britta become growingly concerned about Abed's mental health and enlist the help of Professor Duncan. The group undergoes hypnosis to explore Abed's winter wonderland and soon unravel the truth behind Abed's madness.

When the study group convenes to celebrate Troy's birthday, they realize he is actually turning 21 and decide to hit the bars! While Jeff and Britta ingest a few too many cocktails and get silly, Shirley gets busy pulling down incriminating photos of herself that are posted at the bar. Annie embraces the identify on her fake ID, while Abed delves into conversation with a fellow sci-fi nerd.

When Dean Pelton begins checking class schedules, he discovers that Jeff has listed a class that doesn't exist. Just when it appears Jeff will be caught in a lie, the mysterious "Professor Professorson" emerges from the shadows to confirm that Jeff has been taking his class, "Conspiracy Theories in U.S. History," at night school. When Jeff later admits to Annie that he's never seen Professor Professorson in his life, the two decide to find out who the professor really is. Meanwhile, Abed and Troy are busy building the most elaborate blanket fort that Greendale Community College has ever seen.

When Annie's pen goes missing, she suspects a member of her own study group is the thief. On a mission to find the pen and solve the mystery, the group takes a self-imposed lockdown and Jeff takes the lead in conducting the search. Meanwhile, Troy and Abed are itching to get out of the study room to make it to the Greendale Puppy Parade taking place in the quad.

After a classroom smackdown with a group of "mean girls" led by Meghan, Britta, Shirley, and Annie bond with Abed by turning him into the ultimate "mean girl." Meanwhile, Jeff and Troy embrace a zen-like spirituality under the guidance of a groundskeeper when they come across a secret trampoline on campus. Determined to uncover the source of their new bliss, Pierce ends up taking a disastrous turn on the trampoline and lands in the hospital.

Pierce and a few other Greendale students ingest a biohazard substance at the school Halloween Party, causing them to exhibit flu-like symptoms and begin turning into zombies. It is up to the rest of the gang to save themselves and the school when Dean Pelton locks them in with the zombie-infected student body.

Shirley gets inspired to create a religious film and asks Abed for his creative input only to discover that he wants to make one of his own. Meanwhile, Pierce comes to terms with being the oldest member of the group and is recruited by another set of students his own age.

Dean Pelton decides that Greendale Community College must have its own flight simulator and cannot be bested by the competition, "City College," which is planning its own flight simulator. He enlists the study group to clean and refurbish the Greendale Community College simulator. As Jeff, Pierce, Britta, Annie, Shirley and Troy wash the tattered simulator down, they end up accidentally launching it - sending everyone on an unexpected journey into "outer space." Abed is left behind to try and navigate a safe "return" for everyone.

Pierce deals with the death of his mother and the group comes together to comfort him in his time of need. Professor Duncan struggles to take over the anthropology class with no training, as Professor Bauer takes an unexpected leave of absence after her classroom hijinks put Jeff Winger in the hospital.

When Jeff Winger runs into his former law firm colleague Alan Connor, the two re-connect and Jeff finds himself returning to some of his evil ways of late night partying and expensive suits. Alan takes Jeff to a law firm event to see his former boss, Ted, and the study group shows up to "rescue" him. While Annie, Abed and Troy sneak into the offices to gather dirt on Alan, Jeff watches in horror as Pierce, Britta and Shirley are corrupted by the lawyers.

As classes resume at Greendale Community College for the fall, the "Community" study group gathers to tackle this year's big class, "Anthropology 101. " Television icon and multiple Emmy Award-winner Betty White guest stars as the esteemed, but slightly unhinged anthropology professor, June Bauer. Jeff Winger, struggles to establish decorum with Britta and Annie amidst the confusion that ensued at the season finale's "Transfer Dance," when Britta professed her love for Jeff and Jeff later shared a secret kiss with Annie. Meanwhile, Senor Chang decides to enroll as a student at Greendale Community College so that he too, can join the study group.