That doesn't mean she's just a pretty face. "She's so talented," says her M:I III costar Philip Seymour Hoffman. "I had one scene with her, and she had no lines, but she was incredibly vulnerable. I just remember everyone being blown away." This kind of praise could go to anyone's head, but Monaghan insists she's keeping her distance from the whole Tinseltown thing. "That's my place of work," she says of L.A., "and New York is my home. I like having that boundary. I don't do paparazzi. I don't have actor friends." Sitting in the fanciest hotel in SoHo, she confesses that she'd rather be at Milady's, a nearby Irish sports dive the size of a subway car, where she goes to play pool and watch football.

"Whatever it is that Michelle brings to the party, whether it's being a product of a grounded, wholesome American family or that she's not from the coasts and she's not jaded, she feels like a real person and not like an actress," says M:I III director J.J. Abrams. He took a leap of faith on Monaghan (as he'd done previously with Jennifer Garner), casting her before she'd proved herself in North Country and Kiss Kiss. Abrams had called in Monaghan's reel of clips in a desperate tour through "essentially the SAG directory of everyone," trying to find a virtual unknown "who was going to command the screen with the biggest movie star in the world right next to her, and not disappear." There wasn't much on that reel. Still, he saw what he calls "that secret-sauce thing. She's beautiful, but not the kind of beautiful that you feel is just ridiculous and doesn't exist on the planet. She feels relatable."

Monaghan, who frequently shops at Salvation Army and is, for the moment, wearing a T-shirt her husband designed, is about as anti-starlet as it gets. (She says that after the interview she has to head back to her apartment "to call Verizon and figure out why my phone's not working.") Although she admits to having hired a stylist once or twice, she swears it was only because she discovered that "it's not that easy to go out by yourself and borrow clothes" for a premiere. Still, it's a bit of a shock when she retrieves her coat at the Mercer and out comes this ludicrous puffy thing twice her size, bright red and trimmed with faux fur. What is it, L.L. Bean? "Try Canadian Goose," she says. "It's so not chic, but it's warm!"

Okay, we get it: She's just a down-home girl. But those heartland roots might be the secret to her success. "There's something to be said about the strength it takes to migrate from someplace so unlikely and wind up on the set with Tom Cruise," Downey says. "You really have to believe in yourself."