At 7, Mekhi Phifer played the ghost of Christmas Present in a Harlem Community Center production of A Christmas Carol. But before he was cast as Strike, in the chocolate Moo-drinking crack dealer in Spike Lee's Clockers, Mekhi Phifer (pronounced Meh-kie fifer) had never acted professionally. In fact, he had been accepted into SUNY New Paltz's electrical engineering program when, on a lark, he went to an open call for Clockers, Lee's gritty drama about moral choices in a drug-infested Brooklyn 'hood. Ten callbacks later, he had the lead. "It's nice to do a movie that gets people thinking," "Mekhi definitely knows who he is," says Lee. "He's very talented." Since Clockers, the 20-year-old son of an elementary school teacher has signed for three more films, begun work on a rap album and become a partner in a management company to launch new talent. "He has no chip on his shoulder, no pretensions," says David Zucker, producer of Phifer's next movie, a Rebel without a cause Spoof called High School High. "He just knocked me over.