There's a good possibility Jon Heder would have found a Hollywood career playing sweet, mouth-breathing dorks in slacker comedies even if he hadn't rocketed to dorkdom fame as Napoleon Dynamite who knows? As it is, he's trapped within his comfort zone in School for Scoundrels, loosely adapted from a similarly named, very British 1960 romp of twits starring Terry-Thomas and Ian Carmichael. Squaring off against Billy Bob Thornton, who's in his comfort zone as a sharky, scamming SOB, Heder leads with his trademark toothy expression of clueless stupor as Roger, a meek loser with a crush on Jacinda Barrett's Amanda, the pretty girl in the apartment next door. (Anyone cooler would prefer Amanda's witheringly funny roommate, played by Sarah Silverman.) For lessons in getting the ladies (as well as taking down life's bullies), he takes an underground course from Thornton's shady “Dr. P.” And the lessons work so well that Roger starts to score, kicking in Dr. P's own Bad News Bad Santa competitive side. The clash of comedic styles, meanwhile, dulls Thornton's edge (he can't be mean to such a nebbish and seem fair), while Heder, in his first Hollywood leading role, stalls Roger's energy level as if leery of changing lanes. Director Todd Phillips tries for the kind of frat slaphappiness he applied so successfully to Old School, but these boys are less scoundrels than individual salesmen for the brands of Heder and Thornton.