6D

What do you think about Kastor’s aide not realising it wasn’t Kastor? Any thoughts on this? Was it realistic?

I don't know that it was realistic but because all the cardinals were silent and contemplative it wasn't unrealistic. Unless they discussed something specifically done before Pollux started his impersonation, it would work.

Time was short, Gallo had little time to get ready. His likeness to his brother would be enough for a cursory glance, I believe. Any little things that might appear ‘off’, the aide might be inclined to put down to Gallo being stressed at making the Conclave on time.

Over time he would see through the ruse, but in the short time they were together, i find it plausible that Pollux was successful.

It would make sense, especially as practiced as Pollux was over the course of time impersonating his brother.