What does Will Smith do in the new Bad Boys II? "I carry the big guns," he says, "and show off my muscles. The wife loves that."

Here's betting the wife (that's Jada Pinkett Smith, of course) won't be the only one. The once-scrawny Fresh Prince has been filling out nicely over the years, and in Boys II, which opened July 18, his crime-fighting, butt-kicking hunkitude gets full display. Costar Gabrielle Union certainly noticed. "It's pretty amazing, what he looks like," she says. He's clearly planning to stay that way. On the set in steamy Miami, reports Union, Smith "worked out a lot. At the crack of dawn, while the rest of us were still sleeping, he'd be running on the beach and lifting weights." A boxing fan since he trained for Ali (and packed on 35 lbs. of muscle) in '01, Smith, 34, also "sparred between scenes with his trainer," Union says. "I'd be inside in the air-conditioning and he'd be out there sparring."

So what does the wife—no slouch when it comes to fitness herself (see: The Matrix Reloaded)—have to say? "I love watching him onscreen. He is so super-sexy," declares Pinkett Smith, 31. "It's like looking at another man for two hours and getting turned on, but he's still my husband, so I don't have to cheat."