More than 40 years ago, Eric McMillan, a renowned designer of children's play areas, and his team created the ball pit, those troughs of brightly-colored plastic balls that children swim around in. (Ball pits also may be a giant petri dish of pathogens but, hell, the kids love 'em.) Apparently, McMillan–who went on to be known as the "father of soft play" for his numerous playful innovations like the "punch bag forest"–found his inspiration for the ball pit in his kitchen. From the BBC:
McMillan and his team came up with the idea for the ball pit in San Diego more than 40 years ago, when inspiration struck after looking at a container of pickled onions in the kitchen. "There was a jar of onions, and we were sort of saying: 'wow, how about if you could crawl through those? And then – ding – we decided we'd try it," he says.
The first ball pit, filled with 40,000 balls, opened soon after their epiphany. "People just went crazy about it. Thank God for those onions."
More in this BBC podcast: "Pickled onions inspired me to design the ball pit"