The biggest challenge in writing a review for “Mr. Woodcock” is deciding on a headline — too many possible puns:

1. “Mr.” Thornton’s “Wood” sucks “cock”

2. “Woodcock” too hard to swallow

3. Billy Bob heads “Woodcock”

4. “Woodcock” pulls out instead of putting in

5. “Woodcock” shy of being good

6. “Woodcock”: Block it out of memory

7. Chopping “Wood” better than watching it

8. “Woodcock” not about birds

9. “Woodcock” would be funny, but it’s not

10. “Woodcock” in need of Viagra

…The list goes endlessly on.

This movie — about a sadistic high school gym teacher (Thornton) and the havoc he wreaks — could have actually been good, were it not for the latex-thin sheath of banality that wraps up every scene with an impotent cliche.

Billy Bob Thornton, for one, is the kind of unflinching actor who could ground a risky, original film — much like he did in this year’s intriguing but largely ignored “The Astronaut Farmer” — with steadfast restraint. The pitch, too, had some potential: All the pain and embarrassment of adolescence are called forth with the blast of a silver whistle and the deliberate dribble of a fully pumped basketball. But “Mr. Woodcock” deflates immediately after the first scene — faster than a blowup doll with one too many holes.

Seann William Scott (“American Pie”) plays John Farley, a former fatty turned self-help guru who, while on tour for his bestselling book “Letting Go,” learns that his hometown wants to award him the coveted “Corncob Key.” Farley returns to Nebraska only to find his single mom (Susan Sarandon, in the menopause of her career) engaged to Satan-in-a-red-jumpsuit. Via frequent flashbacks, the audience vicariously revisits Farley’s suppressed memories of torture and humiliation at the hands of his future stepdad. The rest of the film follows Farley’s formulaic struggle: Will he succeed in exorcising Sergeant Evil from his family, or will he take his own advice and forget the past?

To complicate matters further, Farley’s got to deal with his pushy, boozy publicist (SNL’s Amy Poehler), who wants him out of Nebraska and onto the Oprah Winfrey show pronto: “She farts on a book and it sells a million copies,” she caustically iterates. Poehler’s sketch-comedy antics deservedly get laughs, but she seems to be part of a totally different movie than the understated Thornton. Perhaps first-time director Craig Gillespie made the right choice by never putting the two insoluble comics in the same scene.

Annoyingly familiar fluff, though, pervades every, er, inch of “Mr. Woodcock”. Nameless faces playing stock roles such as the disgruntled mayor and the perverted BFF, literally corny jokes like “corn-testants” and “corn-gratulations,” anemic “get in and get out before he comes back” situations — such are the wintered causes of our discontent.

And the many hints that “Mr. Woodcock” has one final trick up its sleeve only disappointingly call attention to the fact that no, it does not. When Farley ultimately confronts Woodcock by asking why he can’t be nice to people, the question goes — as it does throughout the movie — unanswered. What causes a grown man to force pushups on weaklings, laps on asthmatics and public strip-downs on roly-poly preteens? Just whimsy, the film suggests — an answer that’s neither realistic nor much of an answer at all.