Sam was used to Cas randomly appearing, so when Cas and Lydia suddenly appeared in his living room, he wasn't phased by it. He looked up and smiled at the pair of them. His head hurt, as it always did these days, but the pain was tolerable at the moment.
"Hey," he said, greeting each of them at once. "It's good to see you both." He got to his feet and moved toward the pair of them, to greet them properly. In his head, Lucifer stood behind Cas, and after a look toward Lydia, raised his eyebrows suggestively at Sam. Sam ignored his antics, told himself it wasn't real.
"It seems you guys hit it off?" He asked, looking from one to the other. They seemed comfortable enough, or at least not uncomfortable with each other. Sam took that as a good sign.