He was the most popular stand-up comedian of the 1960s. The most successful product pitchman of the 1970s ("Then you dip the spoon in the puddin' …"). The most iconic sitcom dad of the 1980s (and the first with an upper-middle-class African-American TV family). And soon he'll be returning to NBC with a new comedy, perhaps as early as next year. Bill Cosby has been entertaining the world for so long, it's easy to forget how many breakthroughs he has made over a 50-plus-year career — and how many personal tragedies he has endured.