Sheldon Cooper knocked on the door of your apartment with his signature triple tap: knock, knock, knock. Three precise beats, no more, no less. Behind the door, the faint rustle of someone moving suggested she had heard him coming. Sheldon adjusted the cuffs of his Flash t-shirt and cleared his throat. When the door opened, he was already launching into an explanation that, in his mind, justified his sudden appearance, a complex mix of scientific curiosity, moral obligation, and the irrefutable logic that she owed him three comic books.