Few moviegoing experiences are as excruciating as watching two gifted comics struggle with terrible material. Dinner for Schmucks is like an inescapable get-together dominated by humorless palaver and juvenile games, courtesy of people who seem amusing enough at the office but are unbearable for long stretches. But the guilty parties in this case are Steve Carell and Paul Rudd—and damn, it’s hard to watch them squirm.

“Inspired by” the French film Le Diner de Cons, Jay Roach’s comedy pits a reluctant asshole against an enthusiastic idiot. The asshole is Tim (Rudd), a white-collar ladder-climber who feels that, if he wants to get promoted, he must attend his boss’s regular “Dinner for Winners,” which actually is a competition of who can bring the biggest moron. Tim’s incipient good-guy conscience is further reflected by his good-girl girlfriend, an art curator named Julie (Stephanie Szostak), who knee-jerkingly leaves their apartment and, seemingly, him, when he shows even a glimmer of willingness to go along with the cruel gag.

Tim is ready to make an excuse to wriggle out of the commitment when he hits Barry (Carell) in a texting-while-driving accident. (Take note, kids!) On picking himself up, Barry stoops to recover the desirable object he had spotted in the street—a dead mouse to add to his lavish dioramas, which he calls his “mousterpieces.” Not understanding who’s done what to whom, Barry believes he needs to bribe Tim to keep insurance out of the incident. Tim, idiotic in his own way, believes he’s been given a sign. He invites Barry to the party the next night, even after he’s told Julie he wouldn’t go. Then Barry shows up at his apartment that eve instead and immediately begins his destruction.

Excepting bathroom gags (which scripters David Guion and Michael Handelman mercifully avoid), contrived misunderstandings and mouth-breathing whoopsies are about the lowest forms of humor. Dinner for Schmucks is full of both. Tim’s relationship with Julie and his sense of self are pummeled repeatedly, beginning with Barry’s absurdly unbelievable IM-ing with a woman who’s been stalking Tim for years. Barry just happens to sit in front of Tim’s computer and thoughtlessly gives Darla (Lucy Punch) Tim’s address when her online chatter goes from flirtatious to graphic. (Not that it matters, but Tim slept with Darla before he met Julie, and she’s been bugging him ever since.) This leads to more mistakes on Barry’s part, so that Darla winds up in the apartment and Julie finds out. The next morning, Tim leaves for work in a hurry and makes his own fateful mistake, grabbing Barry’s phone instead of his own. And oh no! Barry finds his way into an important business lunch that he then further blows with the intention of helping Tim! And on and on. Har har.

Other mistakes involve Kieran (Jemaine Clement), an eccentric artist whose show Julie is curating. He’s shaggy-haired, egotistical, and plenty weird—and was funnier when named Aldous Snow, a.k.a. Russell Brand’s nearly identical rock star in Forgetting Sarah Marshall and Get Him to the Greek (the thieving is shameless). And don’t forget the main laff contribution of Barry’s eccentric IRS colleague (Zach Galifianakis), which is that he wears a dickey. Will this PG-13 film’s target audience even know what that is?

Amid all the confusion and oddity, it’s up to Carell and Rudd to carry the film, and their strenuous efforts to do so are obvious. Although there are small laughs here and there—it seems the pair’s charisma can’t completely be quashed—Barry is too much of a buffoon and Tim too exasperated a straight man for the premise to work. (Rudd is an even more serious version of his I Love You, Man character, with Szostak playing the same part as that film’s Rashida Jones.) The “idiots” who attend the last-chapter dinner party are intermittently entertaining, but by then, you’re weary and impatient.

Of course, there’s a heartwarming message to the story, instigated by overheard conversations in which people either get their feelings hurt or find out how much they mean to someone. Lessons are learned!

For all the straining and the overhearing and the earnest apologizing, though, the most effective means to deliver those lessons are Barry’s elaborate dioramas. These feature impeccably dressed mice, first in lovely first-date-like outdoor settings and, later, playing out Barry’s sad secret. But they’re so charming, so delicate and detailed, they seem completely out of place in this crude context.