Every time Castle brings Beckett her coffee: It’s such a small gesture, but from the very beginning it was a very real, very subtle thing Castle did that showed his affection for Beckett. Each time they head to a crime scene, he’s got her taken care of. THE COFFEE IS A METAPHOR. It’s love. It’s their hot, steaming, life-fulfilling love. And he was offering it to her even when she didn’t realize she needed it.