When You're Visited By A Copy Of Yourself, Stay Calm

When You're Visited By A Copy Of Yourself, Stay Calm : Krulwich Wonders... : NPR: "You know Carl Linnaeus, right? The great Swedish naturalist who categorized plants and animals in the 1750s? He was a singular figure in botany. But when he got a headache, he stopped being singular. He doubled, from one Carl to two."