Dean's a little scared of how Sam will react, too, partly because he hasn't seen Sam in weeks. They're...estranged. And Dean's been lonely because of it. He's missed having someone in the passenger seat and now that it's Cas over there, he's suddenly feeling a little reluctant about heading back to Bobby or meeting up with Sam and that's nobody's fault but his own.

He notices Cas shoving the pie back in the bag. "Hey--hey, hey, hey! You be gentle with that! Don't you waste pie!"

Because pie is a much easier topic of conversation and Dean is very good at avoidance.