The ASIFA blog asks one of the great ineffable questions, “Who invented the three-fingered hand?” An essay by animation legend Grim Natwick explains:
Someone way back in the dark ages of animation got tired of drawing hands with four fingers and simply left one off, and cartoon hands have been much easier to animate ever since. It was a stroke of genius. The four fingered hand disappeared from animation until “Snow White” (1937). Somehow a pretty girl didn’t look right with only three fingers. But the Seven Dwarfs still had three fingered hands.