HAHAHA! I was deriving the particle-in-the-box solution to Schrödinger’s equation yesterday with my purple pen in class. I was like I could have one pie, two pie, 3 pie, And then I said “all nine kinds of pie just like Harold”. Two-thirds of the class looked at me if I was from another planet. But there were a few that laughed. Read Harold and The Purple Crayon.