Ketchup and Grilled Cheese

Ketchup, Castiel thinks, is not so different from himself. It masquerades as something that could be healthy, has the base ingredients of something that should be, but in the end, it is not. It changes and alters all it comes into contact with. Sullies those it sullies those it touches. And if he were to continue the metaphor, what would that make the grilled cheese? 10x09 coda