Castiel is not what Sam was expecting. Dean had always spoken of him as being a douche, no fun at all, dressed like some pen pusher. When Sam finally meets the angel, he finds himself face-to-face with a sock monkey hat. The kind with flaps that go down over the ears, and long woollen ties that hang asymmetrically past the angel’s collar.
Sam eventually gets his head on straight and stops gaping, and sees that for the most part Dean’s description was pretty accurate. Castiel looks like some tired office worker, he has the most penetrating stare that Sam has ever seen, and he has a voice that is quietly intimidating in its severity.
All of which is made somehow more scary by the hat. It’s like the monkey’s eyes are watching Sam, even when Castiel is deep in conversation with Dean.