I remember reading that when Bob Clampett directed the first Porky Pig episode, Mel Blanc’s stutter was so agonizing that the audience literally squirmed in its seat. This reaction led Warner to adopt what was then a standard practice at Disney: the sweatbox. Walt would get the animation director and whomever was directly involved into a tiny screening room where he would essentially tear apart the day’s work (sometimes several days’ work). This ensured a high-quality end product devoid of such surprises.