maybe im wrong but ever since 12x01 aired i always wondered why cas didnt immediately recognize mary? like i just assumed he would have seen her at some point, in the photographs dean carries, in an angel-fate way, or something.
I mean, he should've recognized her if nothing else than the fact Eve took her form in 6.19, and Cas was there and watched it happen, knew exactly who she was impersonating.
He also must've seen her picture in Dean's room at some point. We know he's spent time in there.
Then again, it's entirely possible he thought it was someone else using her face, the way Eve had. I mean, have you ever seen someone in a place you never expected to see them, and it's entirely jarring because that person doesn't belong here, wtf? Or is that just a me thing?
Like... as a kid, running into your school teacher at the grocery store and being like... wait... how did you get here? And maybe not even being able to place someone out of context like that.
Because Mary certainly didn't recognize Cas, and wouldn't have had any reason to, and as far as she knew she needed to beware of anyone entering that place after they returned to find evidence of a violent altercation.
I think Dabb just wanted to give Dean a chance to formally introduce Cas to Mary. I always chose to see it as Cas allowing that, because also Mary, Dean's mother, had been dead for 33 years and wtf how was she suddenly back? And this makes it into a Meet The Parents trope, which I find endlessly amusing.
I also appreciate that read of the scene, because it allows us to mentally fill in more conversations that we didn't get to see (Dean must've explained some of their lives to Mary before returning to the bunker, and must've explained to Cas how Mary was back and how he was not dead and basically everything that happened in 11.23 in greater detail that we also never got to see).
