Sam looked up at the sound of his name. He was relatively accustomed to Cas appearing out of nowhere, and given the fact that he was in their shared space, it wasn't much of a surprise. He offered a slight smile. "Hey, Cas."
Then he lowered his head back down to concentrate on what he was doing, mid-stitch. When he'd finished it a moment later, he looked up to see that Cas was still there, still watching him. He straightened up more, letting the shirt drape over his lap, the hand holding the needle resting on his knee. "What's up?"