One day, A. J. DiPersia was just another 22-year-old trainee in the William Morris Agency mailroom. The next, thanks to Us Weekly, he was Natalie Portman’s “mystery hunk.” As it turns out, DiPersia and Portman are barely more than intercollegiate acquaintances from Boston (he went to BC, she to Harvard). They bumped into each other at the U.S. Open, which DiPersia was attending with his real girlfriend, a Columbia junior who escaped the paparazzi’s notice. But being mistaken for Portman’s boyfriend has its perks. Family friends, ex-girlfriends, and women who’d rejected him came out of the woodwork. Someone on Metro-North pointed at him, he says, “as though I was someone important!” And an agency higher-up called DiPersia into his office, suddenly interested in his career plans. DiPersia is enjoying the attention: “If you’re coming up from the mailroom, you take any chance you get.” But his colleagues on the bottom rung are rolling their eyes. “No one was impressed,” sniffs fellow trainee Tara Lefkowitz. “And if he was dating her, we’d all pretend not to be impressed.”