[Beware: spoilers]

Homer Simpson, the oafish paterfamilias of America’s favourite dysfunctional family, emerges from his big-screen debut a bona fide Hollywood action hero.

At the start of The Simpsons Movie Homer’s dreams of glory are limited to helping his new pet pig to walk upside down on the ceiling while singing “Spiderpig, Spiderpig” to the Spider-Man theme song.

But when the adopted swine gets him into bigger trouble than even this celebrated screw-up has ever experienced before, he falls under the influence of a chesty Native American woman he calls “Boob Lady” and undergoes an uncharacteristic epiphany that galvanizes him into action for the good of his by-now estranged clan.

By the time the witty final credits roll, Homer outshines even Arnold Schwarzenegger, who has been elected president and ordered great harm done to Homer’s home town.

The Hollywood action theme helps the hit cartoon series, after 18 seasons on television, to land its death-defying leap to the big screen with panache. The result is a postmodern parable about an environmental scare that is at the same time hilarious and horrifyingly poignant. But thanks to an unexpected glimpse of Bart’s genitalia, this is a postmodern parable with a “pickle shot”.

The film boasts the same sly cultural references and flashes of brilliance that have earned the television series a following that ranges from tots to comparative literature PhDs. Despite its clownishness and childish graphics, it still offers searing insights into the pathetic human condition.

When the residents of Springfield learn that they are confronting catastrophe, for instance, the panicked occupants of the bar and the next-door church pour out into the street and change places — the drinkers taking solace in religion and the religious finding comfort in drink.

But the movie will be equally satisfying to those who just find it funny that Homer wants to kiss his pet pig — or laugh at Marge pondering the (literally) weighty issue of the pig’s “leavings”, or excrement.

Early on The Simpsons team shows their nerve by making Homer wonder out loud why anyone would pay to buy a cinema ticket to watch what they could see on TV free — the underlying question of the whole big-screen adaptation. In Homer’s view, anyone who pays for cinema tickets to watch a TV show is a sucker. Jabbing his finger at the audience, he declares: “Particularly you!”

What you get for your money is the Simpsons on an epic scale. The familiar, if geographically indeterminate, territory of Springfield is suddenly transformed into a cross between The Truman Show and Escape from New York, with a Big Brother government conspiring to keep all its unruly residents in line until it can be bombed into a “new Grand Canyon” tourist attraction.

The middle section, set in Alaska, lags because of the absence of the familiar props of the Simpsons’ home town. I found myself longing for Homer and his tribe to return to wreak more havoc on their neighbours, particularly the long-suffering Flanders.

But the film ends with a tense second-by-second countdown that fully exploits the bathos of that schlump Homer becoming an action star able save the world, or at least his little part of it. The conventions of the “disaster flick” allow The Simpsons’ left-leaning creator, Matt Groening, to indulge his politics with wry warnings of environmental doom without boring us out of our mustard-yellow skin.

Lisa, Homer and Marge’s swotty daughter, has become an ardent environmentalist who makes an Al Gore-style presentation entitled “An Irritating Truth” to the local populace.

In the same spirit, this film could have been subtitled: “An Inconvenient Cartoon”.

Matt Groening answers questions about his first feature film in The Knowledge podcast

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