Castiel's expression never changed, though his study relaxed slightly. He had no idea why this man would claim to be a bear, when he was so obviously human, but his tone indicated that he was probably exercising humor. Castiel had started to grasp how to tell when a human wasn't serious, though his expression made it clear he still didn't understand what was going on.
At the question, he blinked. "I watched you interrupt, stop, and defeat these criminals," he responded honestly. At the second question he didn't even bother considering his answer, replying matter-of-factly. "Because some things are evil, and should be stopped. Humans... it isn't easy to tell. You have magic, to see without eyes. You're dressed satanically by the human mythos' standards. You're fighting criminals, without killing them." Castiel took another abrupt step forward, entering the other's personal space obtrusively and intentionally. But apart from the step, he waited patiently. His summary stood, and his intention seemed obvious enough to himself. He wanted to know what this person was, what they called themselves. What their idea of their role was. If it seemed angled towards the side of good, all the better. If it seemed like evil or destructive intent; well... Castiel had new friends in this City. He wasn't sure he appreciated the construct itself, but he had no intent on letting anything hurt the people he'd taken a liking to within it. If that meant patrolling for demons, villains, or simply public gas leaks, so be it.