In his first year in the cast of NBC’s “Saturday Night Live,” Will Forte faced a daunting challenge – taking over an impression of a real person, already made famous by someone else. Former cast member Will Ferrel had nearly perfected his portrayal of President George W. Bush, and when he left, and the president appeared likely to be re-elected, the show needed to fill the gap. Given the popularity of both the performance and Ferrell himself, it seemed like a long shot for Forte. But by his second season, Forte had made the character his own – his whinier, more child-like impression