In Season One, everything is lighthearted and optimistic. The show, possibly split between inadvertent and on purpose, gets darker as the seasons go on. I didn't think about it at the time, but it's true. In an actually unrelated google search recently, I came across an old thread that talked about how depressing Community gets as the seasons go on. Please see The Official /r/Community WIKI.
To write spoilers in comments, use the following format: >!Spoilers go here!< Please try to keep off-topic posts to a minimum! Some of the Community cast members have their own subreddits, so consider posting stuff related to them there instead.