The Study Group consists of the infamous seven characters, but the telling of Community wouldn’t be complete without the Dean or Chang – which sums the main cast at nine. Unfortunately, from episode to episode, not every character maintains their lead/lesser degree, though there is a general scale that they ladder themselves against. Jeff Winger is obviously at the top, most commonly the lead character, and since the beginning of the fourth season, Pierce has been hanging at the bottom of lesser characters.
The Dean is a constant lesser character with more involvement than Pierce but not always as much as Britta through Abed, and until very recently, Chang wasn’t even in the running. However, since his return, Chang is rising the character list – as much as he seems to be edging toward another sinister plot – further displacing Pierce down the rungs. (Guarascio and Port really aren’t hiding the fact that Chevy Chase wants out.)
Among Britta, Troy, Annie, Shirley, and Abed, Britta and Abed seem to take the lead more than the others, and Shirley appears to be grouped more with Pierce as a lesser character. However, these are not always constant and vary greatly between episodes.
The common plot structure, in my opinion, follows this: Jeff sees something he wants and starts for it; by the end of the first third, he is well on his way to succeed; by the end of the second, however, everything has begun to go to Hell in a hand basket, but still Jeff pushes on; and by the final third, Jeff has relented in his pursuit, changed in his ways, normally finishing with an inspirational speech. Then, each episode ends with either a quirky (particularly Troy and Abed) moment or a foreshadowing teaser. (In the episodes that Jeff is not the main focus, the plot still tends to follow this curve, a moment of catharsis wrapping everything up.)
On the whole, each episode stands apart, the conflict resolved by the end, but occasionally, the story line will stretch between two episodes. What’s more frequent is revisiting a story line or way of storytelling in episodes that are not consecutive, even across seasons. For instance, there are several stories told in documentary styles, emphasizing Abed’s love of filmmaking – like the most recent episode “Advanced Documentary Filmmaking.”