My father is a cardiologist. When I was little, he was first completing his training, then establishing himself in practice.
Under both of those "low man on the totem pole" scenarios, his work schedule was brutal; he was on call every other night and every other weekend for years, and while on call spent most of his time in the hospital. So much so, in fact, that, according to my Mom, I once mistook the Ice Cream Man for my father, because his white coat looked like a doctor's lab coat. (My mother assures me the Ice Cream Man was NOT my father!)
So time with Dad was a rather rare and precious commodity. Over a span of years, I tended to think of him as two people: work Dad and vacation Dad. Vacation Dad was a really fun guy. Work Dad was generally a bit scary and given a rather wide berth.
But vacation Dad wasn't limited to vacations per se. There was a bit of vacation whenever he had a weekend or evening off. And among my earliest and fondest memories is an invention of my Dad's that was tailor-made to turn just a few minutes of down time into a treat: up-dee-do!