Once upon a time, only major historical figures like Thomas Edison or Earl Warren were considered worthy documentary subjects. Nowadays, it's enough to be a major-league kook (see Timothy Treadwell in Grizzly Man and Burt Pugach in Crazy Love). This week's model is Dr. Emanuel Bronner, a German-Jewish chemist who immigrated to the U.S. in 1929. He developed a peppermint "pure-Castile" multipurpose liquid soap after the war that, two decades later, found its way into every hippie's bathroom. It was (and is) a fine product, but an essential part of its allure was the label, crammed with microscopic, mysterious text spouting Bronner's All-One-God philosophy. Sara Lamm's Dr. Bronner's Magic Soapbox is an entertainingly loopy portrait of the most eccentric figure in American household-products history -- the FBI labeled the good doctor a psycho case, and who could disagree with the expert analysis of J. Edgar Hoover's boys? But the film also achieves more: When it shifts focus to Bronner's odd-duck son, who now runs the company, Dr. Bronner's strikes some unexpectedly poignant chords.