Crowley's grin is practically wolfish as he kisses his way down, switching to gentle and likely ticklish affection. He's tempted to keep teasing, but he does think he should reward Castiel for trying at this stage of the game. Besides, if a few well-places kisses have him this wound up, what will Crowley's mouth do to his other parts?

He wraps his fingers around the shaft of Castiel's cock and licks the head, never taking his eyes off of Castiel's face.