The extra onions and pie banter - what a great way to have the boys being brothers, clearly back in step with each other after the separate traumas they endured in "WIaWSNB," and also to remind us that the little things stay true, even after changes (switching out the Impala's plates, ditching the credit cards) have been made.
I really enjoyed seeing Sam take charge with all the special kids. He wasn't bossy or arrogant; he just saw that someone needed to take charge and he did it. Possibly what Sam might have been like as the older brother?
And we also got the sort of flip side to that when Andy beamed images into Dean's brain. I guess now we know what kind of "I'm having a VISION!" faces Jensen would have made had they kept him as Sam.
ALSO - the thing with Mary. Am I alone in thinking maybe that moment of recognition was something the YED manufactured to further confuse Sam into thinking that joining the YED is his destiny? We've only seen Mary recognizing the YED from the YED's POV, after all.
Oh, the ending! We finally get our hug. And the preview with Dean's completely red eyes!