Handiwork: "World's Greatest Dad"

Bobcat Goldthwait always was one of the least ingratiating of stand-ups - lumped in with that original wave of anti-comedians - and his directorial CV to date has proved every bit as strident, displaying a marked preference for material that ventures some distance beyond the pale. His 1991 debut Shakes the Clown centred on an alcoholic children's entertainer (played by Goldthwait himself) framed for murder; a notable critical and commercial flop, it led to fifteen years passing before Goldthwait's second feature, 2006's Sleeping Dogs, a no less weird one about a young woman trying to come to terms with a regrettable lapse in her past. Just as that follow-up centred on an outré sexual act - coyly encoded in the film's title - Goldthwait's latest, World's Greatest Dad, is perhaps the only release where the IMDb keywords might legitimately include the phrase "fatal wanking accident".

Here we find Goldthwait setting out to deconstruct the PG-rated family flick that's been so in vogue these past three decades, with the aid of some especially resonant casting. Robin Williams - yes, that Robin Williams - plays Lance Clayton, a dweeby poetry teacher and failed author unreservedly hated by Kyle, his podgy, greasy, porn-addicted ingrate of a teenage son (Daryl Sabara, formerly one of the Spy Kids, circumventing with one, ahem, stroke the usual problems connected with child actors making the leap to adult material). In the likes of Jingle All the Way or The Spy Next Door, dad traditionally has to find a way of proving himself worthy of his offspring's affections; in World's Greatest Dad, Williams does, too, but the character takes an unusual - some audiences may find challenging - route to get there.

For a start, Kyle's fondness for auto-asphyxiation soon gets the better of him: in the tenderest rearranging-a-incident-scene ever filmed, Lance restages Kyle's passing as a dignity-sparing, trousers-up hanging, penning a phony suicide note to go with it. This, naturally, turns out to be the best-received piece of writing of Lance's career, sympathy for Kyle's demise landing him both the colleague he's always wanted to sleep with and the respect of his otherwise unruly pupils. The suicide note also bestows upon Kyle the wholly unmerited reputation of a unheralded literary genius - nay, the voice of his generation - and plans are soon afoot to publish his (dad-faked) diary, under the billing "the biggest posthumous autobiography since The Diary of Anne Frank".

There are a few tonal hiccups early on, as Goldthwait settles into a very particular comic groove, but otherwise World's Greatest Dad marks a significant improvement on the director's earlier films, which played like envelope-pushing ideas in dire need of development. Kyle's death allows Goldthwait rein to dramatise some spectacular hypocrisies: the jock who made Kyle's life hell now vows to win a game in the dead kid's honour, while the headmaster previously pushing to include the deceased in a special needs class insists Kyle "was not slow... he was just brilliant". At the film's centre is a perfectly pitched Williams performance, avoiding both the unbearable sincerity of Patch Adams and the intolerable wackiness of, well, Patch Adams, whether conceding that Kyle's atypically above-the-belt prose is "a little light on the felching side", or squirming his way through a television talk-show appearance that comes this close to exposing the cover-up once and for all.

You could question how ironic Goldthwait's constant recourse to musical montages is intended to be, but these sequences connect a fair bit of funny business, like the publishing guru who seems to speak only in similes (on the heat being generated by Kyle's diary: "it's like a volcano on the sun"), and the unlikeliest celebrity cameo of the year. (Sorry, but that's just the way it is.) In the end, the film isn't the grand satire it might have been - Goldthwait doesn't, as yet, have the resources of a Billy Wilder at his disposal, and the finale, a countercultural rewrite of all those PG-rated "to thine own self be true" conclusions, isn't quite forceful enough - but it is getting at something knotty and pertinent: our continuing desire for the creation of false idols, and our addiction to such grief as might cloud all our better judgement.

World's Greatest Dad opens in selected cinemas today.