From PEOPLE Magazine Click to enlarge
With no help from Donald Trump, Mary-Kate and Ashley Olsen have become New York's latest apprentices—Mary-Kate working with famed photographer Annie Leibovitz; Ashley with top fashion designer Zac Posen—to earn credit at New York University this semester. Though the freshmen already head a $1 billion business empire, each is completing an internship as part of her curriculum at the university's Gallatin School of Individualized Study.

The twins, 18, have previously worked with Leibovitz, whose celebrity photographs often grace glossy magazines, in the Got Milk? advertising campaign. She also shot them for an A&E Biography ad. Ashley, a regular in the front rows of New York's fashion shows, has been a fan of Posen's and his couture creations, seen on the likes of Natalie Portman and Claire Danes.

"[Leibovitz and Posen] were people they wanted to work with," says a friend of the Olsens', adding that they will attend their internships about once a week. "Ashley is very interested in fashion and what Zac is doing. Mary-Kate is very interested in photography and painting." Interning for Leibovitz is not the only new duty for Mary-Kate. She recently bought a chocolate-brown Labrador puppy in New York City (in Los Angeles she had Jack, a half-poodle, half-Chihuahua mix). MK won't lack tips for house-training the pup—a few days after getting the dog, she bought the canine guidebook Labrador Retrievers for Dummies.

Adding to their busy schedules, the Olsens have also advanced their fashion-and-entertainment business, Dualstar, by appointing apparel industry veteran Diane Reichenberger as the company's new CEO. But Ashley, for one, still found time to party—dancing at a Manhattan nightclub on March 4 until 2:30 a.m.