Starring Jason Bateman and Melissa McCarthy. Rated R. Now playing

“More isn’t more,” a trendy hairdresser says with a shudder upon spying Melissa McCarthy’s trailer-trash title character taking her 10th dose of hair spray. In this he is utterly wrong, as too much is way too much in the idiotically plotted Identity Thief.

In this frantic attempt to update the 1980s buddy flick with a cross-gender twist, it’s easy to overlook how well it is cast. No one can so unflappably take a fall—or punches, multiple car crashes, snakebite, false arrest, and sexual humiliation—as Jason Bateman, who plays Colorado-based corporate drone Sandy Patterson. Much hilarity surrounds his unisex first name, which gives a plus-sized Floridian, ostensibly called Diana (McCarthy), the chance to swipe (in the old-fashioned sense) all his credit cards.

Her shenanigans quickly bring ruin to the real Sandy and his adorable wife (Amanda Peet) and small daughters, causing him to seek out the fake one with a vague plan for dragging her back to Denver. It then takes almost two hours of surprisingly graphic, if cartoonish, violence, plus a makeover (see above), before Mr. Everyman—cue the piano arpeggios—realizes how much he needed a Diana to shake him up.

Okay, but shake him up from what? Right after we meet Sandy, he quits his odious boss (Jon Favreau) to join a new start-up at quintuple the salary, and his whole clan seems genuinely happy. Director Seth Gordon (Horrible Bosses) and screenwriter Craig Mazin (of the Scary Movie and Hangover franchises) give us zero indication of why the identity in question requires such an extreme, and extremely unfunny, series of wake-up calls.

That’s sad, because every scene taken up with stunt doubles in danger is one that doesn’t take advantage of the natural rhythms Bateman and McCarthy get going when simply allowed to riff off their opposing personalities—surely the reason they took this gig in the first place. They probably didn’t realize just how much “more”—and less—would be expected of them.