‘Mr. Woodcock' is a gym-dandy comedy. Seann William Scott plays a successful author who learns his mother is dating his old P.E. teacher

Contrary to appearances, “Mr. Woodcock” has more going for it than vivid double entendres and a premise ripped straight from the “Meet the Parents” playbook of goofy situational comedy. Not a lot more, but this surprisingly smart riff on the demons of childhood still delivers a more potent comic punch than a mere lobby one-sheet might lead you to believe.

In his first remotely funny performance since “American Pie,” Seann William Scott plays John Farley, a namby-pamby self-help guru riding the success of his new, best-selling book: “Letting Go: How to Get Past Your Past.”

From the outset, we understand John to be something of an unwitting snake-oil salesman - one of the great running jokes in the movie is the never-ending queue of weirdoes and losers who vigorously thank him for “totally changing” their lives.

To his boyish delight, John is invited back to his hometown to accept the key to the city - the “Corncob Key,” it being Nebraska. So against the wishes of his jaded, booze-swilling publicist (“Saturday Night Live” sparkplug Amy Poehler, in another winning bit role), John flies back home into the waiting arms of mother Beverly (Susan Sarandon).

Unfortunately, Beverly bears horrific news (for John, anyway). She is dating his old high school gym teacher, Mr. Woodcock (Billy Bob Thornton), a whistle-blowing Nietzschean tyrant who once delighted in tormenting John's chubby former self.

Working from a compact, inventively funny script by first-time screenwriters Michael Carnes and Josh Gilbert, director Craig Gillespie (he of the upcoming indie romance “Lars and the Real Girl,” with Ryan Gosling) keenly elevates Woodcock's petty abuses to mythic dimensions.

The magisterial lighting, the subtly distorted angles, the salt-and-pepper crew-cut - all of it serves to highlight Thornton's natural authoritarian qualities. Suffice to say, the “Bad Santa” star is spot on. Viewed via John's rueful flashbacks, Woodcock is the closest thing a Midwestern gymnasium has seen to Joseph Stalin, particularly when tells a wheezing student to “Lose the asthma!” before sending him to run laps.

That Woodcock will put John's pacifist, forward-thinking philosophy to the test is a given, as is, I suppose, the scene where John finds himself trapped under a bed while Woodcock makes vigorous love to his mother, or Woodcock's many thinly veiled references to his own sexual prowess: “It's probably good for the old hip flexor to give it a night off,” he jokes, creepily. Less expected, however, is the movie's surprisingly poignant tribute to a generation of single mothers who, in deference to their kids, denied themselves the possibility of romance.

‘Mr. Woodcock'

Stars: Billy Bob Thornton, Seann William Scott, Susan Sarandon

Behind the scenes: Directed by Craig Gillespie from a script by Michael Carnes and Josh Gilbert

Rating: PG-13 for crude and sexual content, thematic material, profanity and a mild drug reference

Running time: 1 hour, 31 minutes

Grade: B-