Richard Fleischer (mentioned below) penned a biography of his father - 'Out of the Inkwell' - that I would thoroughly recommend. It details, among many other things, the development of the Rotoscope. Another fun fact: it was the Fleischer cartoons that prompted Superman's gift of flight - before then he merely fell with style!
Such a level on invention and imagination was applied by Fleishcher in these early 'Betty Boop' cartoons. Miind you a little of Boop can be better than a lot in one sitting. Best here would be 'poor cinderella' and 'blunderland'. 80 years later and would still love to have her figure.
Brother Max gave us Richard Fleischer, one of the great do-it-all directors: "The Narrow Margin" (a stunner), "20,000 Leagues Under the Sea," "Compulsion," "Fantastic Voyage," "The Boston Strangler" (an unsung American New Wave classic, right up there with Frankenheimer's "Seconds"), '10 Rillington Place," "Soylent Green"—plus high and low camp, musicals, etc. Given Dad's cartoons, this makes perfect DNA sense!