Pretty much everything in Community centered around the show's core study group. Jeff, Annie, Britta, Abed, Troy, Pierce, and Shirley were immediately the heart of the series, with the likes of Chang and Dean Pelton being the key players outside of the group. They all debuted as part of the "Pilot" episode.
Of course, Community evolved over its six seasons and was constantly adding interesting characters. Whether they were replacing someone who left the study group, working at Greendale, or were just people who unexpectedly stole their scenes, some of the show's most memorable and funniest characters debuted after season 1.
Vicki
The first time that Vicki (Danielle Kaplowitz) appeared came in season 2's "Intro to Political Science." She was among the people running for student body president, including Pierce, who only ran as a way to get revenge on her for not lending him a pencil.
She ended the episode by stabbing him with a pencil and though people didn't know much about her, Vicki kept popping up over the years. That included taking part in the second paintball game, starting a romance with Neil, and getting annoyed at how Greendale was always seemingly centered on the study group.
Elroy Patashnik
By the time season 6 rolled around, the show was quite different. Along with being on a new network, it had to proceed without Pierce, Troy, and Shirley. One of the replacements to the core group came in the form of Elroy Patashnik (Keith David), who debuted in "Lawnmower Maintenance and Postnatal Care."
Elroy created a virtual reality company and kind of took over the "Pierce" role of the group as the older person who was behind the times. He took a while to really bond with everyone, especially Jeff, before getting a job at LinkedIn in the series finale.
Marshall Kane
One of the most interesting additions to Community was Marshall Kane (Michael K. Williams). Most known for his intimidating role on The Wire, Williams felt like a more serious actor than most would expect to a comedy series. That's what made it work, though.
Kane was the biology professor at the start of season 3, appropriately debuting in "Biology 101." Though he wasn't trying to be funny, he did so by calling out the absurdity of the school and questioning things that he missed while he was in prison, which is where he got his Ph.D. His demeanor was ideal for the Law & Order parody episode, "Basic Lupine Urology."
Sean Garrity
It's hard to nail down the best episode in Community history but a strong contender is "Conspiracy Theories and Interior Design." In it, Jeff made up a night class with a teacher named Professor Professorson. He was stunned when someone actually showed up claiming to be Professorson.
That person was Sean Garrity (Kevin Corrigan), who was actually Greendale's drama teacher. Other than that legendary installment, Garrity also went on to be Britta and Troy's acting teacher and he taught a course on whether Nicolas Cage is a good or bad actor.
Neil
In "Asian Population Studies," Neil (Charley Koontz) was first introduced in quick fashion. However, everyone re him from "Advanced Dungeons & Dragons." There, he was the focal point as the study group invited him to play D&D since they saw he had been down for weeks.
Dubbed "Fat Neil" by Jeff and tormented by Pierce, Neil stuck around until the end of the series. He began dating Vicki, ran a radio show, and kept "doing things in the background." In the end, he wasn't friends with the study group after they forced him to sit through an offensive comedian dissing him.
Frankie Dart
Like Elroy, Frankie Dart (Paget Brewster) ed the main cast during the final season. She was initially brought in as a consultant to help the school in the premiere episode, "Ladders." Interestingly though, the actress appeared in season 5 as Debra Chambers in a small role.
At times, Frankie came across as an older version of Annie as she was intelligent and often questioned the antics of those around her. While she helped them a lot, they also allowed her to become a bit more relaxed as a person. Frankie ultimately helped save Greendale in the end.
Vice Dean Laybourne
Season 3 saw the inclusion of a storyline where Troy was being courted by Greendale's air conditioner repair annex. On paper, it seemed like nothing big but the show went out of its way to make this annex feel special. They held the true power at the school and were downright weird.
It all started with their leader, Vice Dean Robert Laybourne (John Goodman). He immediately proved to be a threat with how he verbally ran down Dean Pelton and continued with the way he instigated Troy and Abed's fighting. Though he was serious, he also had some really funny moments.
Magnitude
"Pop, pop!" It has gone on to become one of the most iconic lines relating to Community. Those are the only words uttered by Magnitude (Luke Youngblood) in the series and it became something that every fan brings up to this day. Magnitude got his name from having a "magnetic attitude."
He first showed up at a gathering at Jeff's house because he was the "one-man party." From that point on, Magnitude was constantly around to deliver his line in hilarious ways. From the debate against Leonard to not being able to finish the saying after a paintball explosion, Magnitude was always a highlight.
Rachel
Most fans agree that season 4 was the show's low point and even the cast and crew call it the "gas leak year." One great thing that came from it was the arrival of Rachel (Brie Larson). In "Herstory of Dance," she was the coat check girl at a party who met Abed while he was on a date with two women.
She helped him with his shenanigans and they ended up bonding. Rachel returned as Abed's girlfriend in later episodes and the two had a fantastic dynamic. She was just as odd as him while also fitting in with the group. It's just a shame that she only appeared in a few episodes.
Buzz Hickey
Season 5 began in turmoil as it had to address Chevy Chase's departure while bringing back Dan Harmon and introducing someone new. That new character was Buzz Hickey (Jonathan Banks), a criminology professor who became friends with Jeff once he became a teacher.
Hickey ed the Save Greendale committee and though he was a crotchety old man, he had his quirks. He engaged in the wackiness of the group like the Floor is Lava game and he was an amateur cartoonist. Hickey's unique personality seemed out of place with the rest of the gang but that's exactly why he fit in.