Stephen Levinson, who has served as actor Mark Wahlberg's manager and producing partner for almost 20 years, is also the award-winning producer and writer of the critically-acclaimed HBO series "Entourage" and "In Treatment. " Levinson moved from New York City to Hollywood in the early '80s and soon landed work in the mailroom of a talent agency. After striking up a friendship with Wahlberg, the two decided to collaborate on a show based loosely around their adventures as two young, single guys living in status-obsessed Los Angeles. What they came up with was "Entourage," a sweet but snarky show that follows the misadventures of rising film star Vince Chase (Adrian Grenier) and his tight-knit crew of friends as they navigate Hollywood's cutthroat waters. The show's enormous popularity and success led Wahlberg and Levinson to serve as executive producers on another HBO show, "In Treatment," a tense and unsettling look at what happens behind a therapist's closed doors. Levinson had a big 2010; he helped create "Boardwalk Empire," HBO's high-profile and star-studded series set in violent and corrupt Prohibition-era Atlantic City, and executive produced the scrappy "How to Make It in America," about two streetwise friends (Bryan Greenberg, Victor Rasuk) trying to make it big in New York City.