bahah he'll probably just ping the way the kithain (humans related by blood to fae but not actually fae) do: you're weird and human but not completely. But poor Cas :c actually with the amount of drinking/getting high he does he might have all kinds of weird little loopy echoes brought on by consistent drunkenness and hallucination, so that would be interesting.

D'you think there's a possibility Lucifer!Sam might turn up in his echoes?