Sometimes it feels like Robin Williams is the source of all the melancholy in the world. You know? Like the Fates took all the joy that Robin Williams ever possessed or would possess and wove it into one magical pair of rainbow suspenders, which were stolen by a witch some time in the early 1980s, forcing him to transition into Adult Human Pants (held up by the Belt of Gloom), leaving nothing inside but a vacuous, suspender-shaped quarry of despair. And we all. Might. Fall. In.

I have never met the man. But I have felt the suck of his sadness through the screen in World's Greatest Dad, a brutally bleak comedy written and directed by Bobcat Goldthwait. In it, Williams (beautifully cast, for the aforementioned reason) is Lance Clayton, single father, medium failure ("I am a writer"), and unpopular high-school poetry teacher. When his teenage son, Kyle, a cruel, sex-obsessed asshole (kids really are a bunch of manipulative shits, aren't they?), dies autoerotic-asphyxiatorially, Lance tries (out of love, because this is what parents do) to salvage his offspring's reputation. He forges, in Kyle's name, the diary of a tortured poet who never existed at all, Kyle becomes a sort of high-school folk hero (an empty vessel for other students' everythings), and Lance gets a book deal and a crisis of conscience.

World's Greatest Dad is rough, funny, smart stuff. Even Lance's tiny successes have a pathos that's almost too sad to bear (his pinnacle is a series of greeting cards with the slogans "I'm not monkeying around!" and "I'm not pussyfootin' around!"). And Williams punches you right in the gut with that pathos. This is a trudging, good movie.

Due to the vagaries of Hollywood, we ran this review a week early. The actual opening date for World's Greatest Dad is Friday, September 4.