Ivan Shreve has a great post about character actor and writer George Furth, who died at the age of 75. (And I'm not just saying it's a great post because Ivan says nice things about me in it.)
His most famous credit as a writer was of course the musical Company, which he didn't intend as a musical at all; he wrote it as a bunch of unconnected playlets about marriage, at a time when there were a number of successful short-play collections running on Broadway. (Neil Simon had done Plaza Suite with George C. Scott playing the lead in three different short plays, while Robert Anderson had done You Know I Can't Hear You When the Water's Running, four short plays in one evening.) Instead it became the guinea pig for producer-director Hal Prince's big experiment, an attempt to do a musical with no linear storyline, basically an evening-length version of the story-breaking bits from earlier Prince musicals like Cabaret. Furth linked together some of the unrelated playlets with a lead character, the committment-phobic Robert (this explains why Robert doesn't actually do a whole lot in the show; he's mostly watching sketches that weren't supposed to involve him in the first place), Stephen Sondheim wrote songs that commented on the themes of the evening instead of directly telling the story in the Rodgers and Hammerstein tradition, and choreographer Michael Bennett did some of his best work (this and Follies were the last time that Prince or Sondheim would ever give a choreographer a chance to really express his personality, and their later Bennett-free musicals cut dancing to a minimum).
The result was a rallying cry for people who wanted the musical to "grow up," but perhaps more importantly, the result was an actual money-making hit, one of the few Prince/Sondheim shows to make a profit. Furth was brought back for the last Prince/Sondheim show, the rather dismal Merrily We Roll Along (yes, it has some good songs, but some not-so-good ones too, and nothing else in the show worked), but Company, with its famously cryptic dialogue -- lines like "A person like Bob doesn't have the good things, but he doesn't have the bad things, but he doesn't have the good things" -- is his biggest claim to fame as a writer.