Born in Massachusetts and educated at Harvard, this self-consciously geeky redhead began his career off screen as a comedy writer for Saturday Night Live and The Simpsons. When he was tapped to replace David Letterman as the host of Late Night in 1993, he was virtually unknown to audiences, with only a handful of on-camera SNL bits under his belt. Although it took a while for his talk show to pick up steam, eventually it became a juggernaut. Based on his success, NBC announced in 2004 that O'Brien will succeed Jay Leno as the host of The Tonight Show in 2009.