American Fable is ambitious, maybe too much so sometimes, but there's an intense pleasure in the boldness of the film's style.
The Simpsons are fairly surprised to find themselves in a movie; they can't believe "anyone would pay to see what we did on TV for free." But I suspect a lot of people will. Here is a feature-length version of what Time magazine, no less, called "the 20th century's best television series." That may say more about Time magazine and the 20th century than it does about the Simpsons, but never mind: The movie is funny, sassy and intelligent in that moronic Simpsons' way.
There is a plot, sort of, involving Homer's role in polluting the lake in Springfield, which calls down the wrath of the federal bureaucracy and leads to dire consequences for their fellow citizens. The Simpsons' guilt is counterbalanced by poor, idealistic Lisa, who goes door-to-door collecting signatures for her environmental crusade, only to get every door slammed in her face. One house even flees.
This story allows room for the sorts of political asides "The Simpsons" are famous for; not broadsides, but sideswipes. When the feds finally succeed at something in the movie, they're as surprised as everybody else.
For me, the three biggest laughs in the movie (I won't spoil them) are a plug for the Fox network, a skateboarding sequence inspired by "Austin Powers" and a unique way to go fishing. Those, and the peculiar everyday lives of the closely knit Simpsons, fill in the gaps in the plot, along with a devout neighbor who, considering what Homer puts in his mailbox, is more sinned against than sinning.