Editor's note: This review may contain spoilers.
(CNN) -- Melissa McCarthy didn't quite come out of nowhere.
The actress did seven years of "Gilmore Girls," headlined "Mike & Molly" for CBS and played three roles in screenwriter John August's ingenious first feature as director, "The Nines." But her supporting turn in "Bridesmaids" was a revelation, a powerhouse comic performance that pushed that movie to another level of hilarity. In recent years, perhaps only Zach Galifianakis in "The Hangover" has had a comparable impact. McCarthy was lewd and fearless, a woman unashamed of her size and her sexual appetite.
How to follow that? There's no question she represents a challenge for Hollywood, not only because the industry still struggles to believe women can carry movies, but also because screen glamour is synonymous with thin.
Her first star vehicle, "Identity Thief," is not likely to be remembered as anyone's triumph (it's scoring in the 20-something percentile on the critics' aggregator site Rotten Tomatoes), but at least it does enough to show that McCarthy has what it takes. If she forges a movie career, she could really shake things up.
She's not quite flying solo, of course. Jason Bateman has top billing as Sandy Patterson, a financial officer in a big Denver firm. When reports start coming in that he's maxed out his credit card in Florida, Sandy is naturally upset. Turns out McCarthy has stolen his identity and is running up big bills on all his accounts. Oh, and she's missed her court date, which means there's an arrest warrant out in his name.
Mustering enough cash to fly down there, Sandy decides to apprehend the imposter himself and escort her back to Colorado so that they can straighten out the mess before he loses his job and his home. She may be a scam artist, but Sandy reckons she looks harmless enough.
And that would be his fatal error: If there is one thing McCarthy means to prove, it's surely that one look is not enough, because there is so much more to her than meets the eye. In one of the movie's better running gags, she proves it again and again when she delivers a vicious sucker punch to the throat of anyone foolish enough to threaten her well-being.
McCarthy, as Diana (which may or may not be her real name), is not about to give up without a fight. But she's also slippery in more subtle ways, an operator who knows how to manipulate people with the way she looks and how she talks. In some cases that involves playing on their pity -- and on ours, too, as the filmmakers imply that her weight is a symptom of her unhappy life. But McCarthy has the personality to subvert this, because her Diana may be lonely, but she is still more vital, more spontaneous and more fun than Sandy is ever likely to be.
In the best, most daring sequence, she picks up a guy in a bar (Eric Stonestreet as Big Chuck) and persuades him back to their motel room to have sex with her in front of her husband, Sandy, who "likes to watch." It's all a ploy to make an escape, but the scene pivots -- Big Chuck makes it about emotion, not sex, and she responds to his openness. Then things get physical. McCarthy pulls off these shifts with gusto but also delicacy and, yes, tact.
In a sharper movie (and let's shoot for the moon here -- Barbara Stanwyck as the con woman in "The Lady Eve"), Diana would play Bateman's smug executive for a sucker and take him for everything he's got. But in these recessionary times, even financial officers can be sympathetic underdogs, and instead the film contents itself with puerile cracks about his manhood and undeveloped hints that her bad influence might rub off in a good way.
Written by Craig Mazin ("The Hangover Part II") and directed by Seth Gordon ("Horrible Bosses"), "Identity Thief" borrows too much from the likes of "Midnight Run" and "Planes, Trains & Automobiles" without giving enough back -- especially since "Due Date" already went that route quite recently. But even with all its shortcomings and sentimental fudges, there is something about McCarthy's refusal to lie down and play the victim that gives it a comic edge.
A blunt edge, to be sure, but an edge all the same.