Tipping the Spherical Cow
Madeleine's cartoons are listed here. Her site, Tipping the Spherical Cow, surely takes part of its name from an old scientific joke. I first read this in the book A Random Walk in Science, reviewed on Amazon; here is one version:
Worried by the ever-rising cost of animal feed, a dairy farmer hires three consultants — an operational researcher, a nutritionist, and a pure mathematician — to tell him how to increase his profits. They spend a day looking around the farm, and then go off to write their reports.
Two weeks later, all three reports drop through the farmer's letterbox. He opens the operational researcher's report, to see page after page of meticulous diagrams showing how to optimise fodder crop layout for easy planting, and timetables for staggering breeding dates to even out milk production across the year. He opens the nutritionist's report: detailed lists of grass varieties, carefully sorted by seed price, rust-resistance, and usefulness as silage. He opens the pure mathematician's report and reads the first paragraph. It begins "Consider a spherical cow".