"Community" (NBC, Thursday). The low-rated and much-beloved comedy about a study group at a community college that is not about a study group at a community college so much as it is a comedy about a comedy about a study group at a community college that is only incidentally a study group — and so on — concludes its fourth and possibly last season this week. (The first without cashiered creator and showrunner Dan Harmon, it was delayed from October to February, with the odd effect of airing its Thanksgiving and Christmas episodes in early spring.) At some point in its first year the show jettisoned any pretense of sticking to its premise and embraced its true nature, as an avant-garde meta comedy that, at its best, plays with form and content with an almost childlike glee. (It's actually more of a meta-meta-comedy, which takes note of its own awareness of its awareness — and so on.) That's a tough thing to pull off week after week, season after season — after you've proved you can do anything, and have done it again and again, some of the thrill is bound to be lost — and there were times this year that the show seemed unfocused and obvious. In trying to find a way between invention and feeling, it could grow conventionally, rather than unconventionally, sentimental, or too eager to point out the smart thing it was doing. But it has been finding its feet again: There have been fine, surprising episodes of late — the puppet musical, the one in real time — and its ensemble is one of TV's greatest. See it now.