One recent morning on the Charles Bridge, which spans the Vltava river in Prague, a middle-aged portrait artist with a gray ponytail was sketching the tourists who come here to experience a European destination that’s billed as the City of a Hundred Spires. To advertise his skills, he has displayed a selection of his drawings of celebrities. The portraits are recognizable, but each is oddly off-kilter: A bloated Johnny Depp is pinned next to an intoxicated-looking Cameron Diaz, which is above a J.Lo who appears to need radical intervention from an orthodontist. In the place of honor—positioned next to the artist himself, no less—is a portrait of Angelina Jolie and her partner, Brad Pitt.

The unfortunate sketches are a reminder that for the past few weeks Prague has been home to Pitt and Jolie, whose presence has made this capital—so pretty it could have been concocted by a pâtissier—the red-hot center of the celebrity universe. The couple’s effect on the city is not lost on Pitt, who, playing the role of Mr. Mom while Angelina films the thriller Wanted, faces the same paparazzi assault he would in L.A. as he drops Maddox off at the Élysée school and shepherds his other three kids around. (In case, like Brad Pitt, you’re not a reader of US Weekly, the roll call is: Maddox Chivan, 6; Pax Thien, 3; Zahara Marley, 2; and Shiloh, 1.)

Brad Pitt enters the room at a clip. Like he’d better not stop moving, like there might be something following him.

“Hi, I’m Brad.” The handshake is firm, the forearm wiry. He wears a khaki-colored long-sleeved T-shirt with another, short-sleeved T-shirt over the top, corduroys, and suede ankle boots. There’s a cream-colored felt fedora on his head. During our conversation he will shift the hat to several different places on his crown: Sometimes it will be perched on the back, like he’s a Thompson Twin; other times it will be cocked to the side, P.I.-style; but most of the time it will sit in the middle, hiding his precisely cut hair. He will lift it occasionally and run his hand through a mane that has been dyed the color of a Hershey’s Kiss.

Pitt slings a messenger bag that’s packed with stuff—it could be the bag of an eighth-grade boy who hasn’t cleaned it out for a couple of semesters—on the couch.

“I’m just about to fall over,” he says. He has the humming energy of a guy who has just got to eat. “I’ve got a mad metabolism.”

He scans the menu. “You can go to any country in the world, and you order a club sandwich, and universally it’s always a safe bet. It will not fail you,” he says, hunching over the black binder. He orders spaghetti Bolognese anyway, apologizing for sticking me with the bill despite the fact that, he admits, he has a pocketful of Czech crowns. When the food arrives, after slicing it into small pieces, he devours most of the spaghetti standing up (“I’m a father, I rarely get to sit down and eat”). Occasionally he will sit on the floor, his legs extended under a glass coffee table. Other times he will squat, bouncing on the balls of his feet. Here he is, Brad Pitt, a hungry American eating Italian food in the Czech Republic while plotting to save the world.