"So, would it be inappropriate if I were to sing right now? The singing in the film, it's because they are happy and I too, cannot find the right words to describe that." Castiel genuinely wondered this, because he thought it was fitting. After all, Meg made him happy, made him feel a lot of different things that he'd yet to truly figure out when it came down to it. He might not understand all of the emotions he felt and what he was and was not ready for, but he knew he wanted things with Meg, albeit he didn't know to what extent and what those things just might be. But, by the standards of the film, he assumed that he could figure out a way to sing and that would make it easier to express what he was feeling inside and how that made him feel as a whole.
Just the slightest hint of a smile, that one he reserved for Meg alone, appeared on his features when she splayed her hair out, reminding him of his earlier task. "Are you not going to watch the rest?" His question was curious, not understanding why she turned away from the television, but glad for the fact she was giving him the chance to continue to play with her hair. He rather liked it, as strange as that sounded, because he didn't get to do something so... simple and mundane as this and actually feel content about it. He wasn't doing anything beyond running his fingers through her hair, an act that didn't take much, but it didn't create that frustration of being idle within him.
As his fingers ran through her hair and he shifted his focus between Meg and the television, the screen flickered and the hum of the electricity died out, resulting in the room going pitch black because of the power going all because of the storm. It didn't cause alarm in Castiel, although it was disappointing to no longer have the television. He would now miss the ending of the film and that was disappointing.