Book excerpt: Nancy Cartwright, the ultimate Simpsons insider, gives voice to the boy immediately recognizable as none other than Bart Simpson. Now, Nancy traces The Simpsons rapid rise to wild popularity, offers hilarious anecdotes about cast members and guest stars and reveals what its like to be at the center of a North American institution, one that reinvented the sitcom, rocked the networks to the core and forever changed the face of television.