it just sort of happened. The animation had changed (became cleaner), the color palette had changed (brighter and, dare I say it - a bit annoying) and, most importantly, the style of humor had changed. In a way, it became a show about Homer's crazy hijinks and him acknowledging that fact. While earlier seasons were more about deconstructing the mundane, american suburban life and making it universal (so that kids like me, thousands of miles away in a different country could still understand and see his own life partially reflected), the newer seasons were zanier, more blunt, even more self-aware.
In this vein, I'd like to say an extremely unpopular opinion: "Homer's Enemy" has never been one of my favorite episodes. I know why some people love it and I have no quarrel with others putting it on their favorite episode's lists - I know I'm in the minority here. I just find the episode's final sequence really morbid. And no, this wasn't the start point of "Jerkass Homer" as some would try to say: Homer was, actually, good-intentioned but oblivious during the episode. He wasn't trying to be actually an asshole to Frank Grimes. "Jerkass Homer", on the other hand, was very much conciously an asshole just "for fun" (if he were an internet user, he would say "for the lulz"). It just... doesn't sit well with me. It was like a moment in which the series finally starting acknowledging its own wackier elements and, slowly but surely, would begin to flaunt them in flashier ways. Season 9 was a bit of a dropoff from the previous year (with good moments), Season 10 was more of a dropoff and then Season 11... was the point in which I was ready to leave the show behind. There are still good (even great) moments from that point onwards, but the series, as a whole, had declined so much it wasn't even worth the hassle to wade through the mud to find a small gem.
So, in a way, I would agree with some previous posters about "Homer's Enemy" being a good season finale. It was more meta than the Poochie episode because while that episode had flirted very passionately with breaking the fourth wall, it remained a biting satire on the entertainment industry as a whole - "Homer's Enemy" was much more a satire of itself, a comment on the very nature of the series: how this boring, mundane american life was anything but... and how the lovable loser who seemingly hated it, realized he actually didn't.
