All the usual disclaimers apply: I don't own Castle, never will, and certainly have no chance of ever profiting from it. Thanks go to ignacio2012 for the prompt.
Evolution
She looks at him thoughtfully. "You're not the same person you were when we first met."
"No, I'm not," he agrees as he takes a cautious sip of his too-hot coffee. "Is that a good thing, a bad thing, or just a thing?"
She considers the question. "A good thing," she says eventually. "Seeing the things we see, doing the things we do...any sane person would be affected by that, but not always for the better."
"Careful," he warns jokingly. "That sounded suspiciously like a compliment."
"Yeah." She knocks his elbow off of her desk. "I must be slipping."