This article goes something like this:
In a discussion with Grothendieck, Messing mentioned the formula expressing the integral of $\exp(-x^2)$ in terms of $\pi$, which is proved in every calculus course. Not only did Grothendieck not know the formula, but he thought that he had never seen it in his life.
But how does a great mathematician like Grothendieck hear nothing about the Gaussian integral? How is it possible to explain this?