Follows the four high-profile productions that would eventually become Tony nominees for Best Musical of 2004: “Wicked,” (currently the highest grossing musical of all time), the Rosie O’Donnell/Boy George musical brought from London, “Taboo,” Tony Kushner’s “Caroline, or Change,” and a grown-up puppet show called “Avenue Q.” Digging behind the scenes, from casting and out-of-town previews to the suspense-filled Tony Awards, “ShowBusiness” provides an engrossing look at the inner workings of Broadway musicals. Listening in to critics around the dinner table, interviews with the creators, footage of rehearsals and openings all combine to make this one of the most entertaining documentaries (and dramas) about the world of musical theater.